Pertussis Outbreak: The Family Practice

1. Pertussis Outbreak:The Family Practice / Public Health Team D.C. Krulak, MD, MPH LCDR MC USN

2. Introduction Epidemiology Case overview Pertussis is a highly communicable disease with secondary attack rates of 80% or more among susceptible contacts. Prior to the availability of vaccine pertussis was a significant cause of morbidity and mortality among children. With the advent of universal vaccination, incidence rates dropped from 150 per 100,000 population to as low as 0.5. However, cases have been on the rise with incidence rates now reaching 4 per 100,000 population. Presented is a case of the community response to a pertussis outbreak in Camp Lejeune, NC. From initial detection, to case management, to prevention of further spread, family physicians were an integral part of the public health team. Their interventions aided in preventing this outbreak from detrimentally impacting the operational forces assigned to the base. -------------------------------------- Pertussis is a highly communicable disease with secondary attack rates of 80% or more among susceptible contacts. Prior to the availability of vaccine in the 1940�s, incidence rates were approximately 150 cases per 100,000 population; and pertussis was a significant cause of morbidity and mortality among children. With the advent of universal vaccination, incidence rates declined as low as 0.5 cases per 100,000 population in the mid 1970�s. However, pertussis has been on the rise since the mid-1980�s with incidence rates of 4 cases per 100,000 population. Infants less than 6 months old still comprise the largest proportion of cases, but adolescents and young adults have accounted for a dramatically increasing share. Reasons postulated for the resurgence of pertussis are varied. The bacteria may have experienced genetic drift in a way that reduced vaccine derived immunity. It is possible that historical prescribing practices may have led to antibiotics given in the early stage of pertussis, thinking they were viral URIs. With the current stress on avoiding antibiotic overuse, physicians may inadvertently allow the full development of the disease. Alternately, the incidence rate increase may be due less to disease factors than an improved reporting system and increase in case detection. Presented is a case of the community response to a pertussis outbreak in Camp Lejeune, NC. From initial detection, to case management, to prevention of further spread, family physicians were an integral part of the public health team that stepped forward. Their interventions aided in preventing this outbreak from detrimentally impacting the operational forces assigned to the base.Pertussis is a highly communicable disease with secondary attack rates of 80% or more among susceptible contacts. Prior to the availability of vaccine pertussis was a significant cause of morbidity and mortality among children. With the advent of universal vaccination, incidence rates dropped from 150 per 100,000 population to as low as 0.5. However, cases have been on the rise with incidence rates now reaching 4 per 100,000 population. Presented is a case of the community response to a pertussis outbreak in Camp Lejeune, NC. From initial detection, to case management, to prevention of further spread, family physicians were an integral part of the public health team. Their interventions aided in preventing this outbreak from detrimentally impacting the operational forces assigned to the base. -------------------------------------- Pertussis is a highly communicable disease with secondary attack rates of 80% or more among susceptible contacts. Prior to the availability of vaccine in the 1940�s, incidence rates were approximately 150 cases per 100,000 population; and pertussis was a significant cause of morbidity and mortality among children. With the advent of universal vaccination, incidence rates declined as low as 0.5 cases per 100,000 population in the mid 1970�s. However, pertussis has been on the rise since the mid-1980�s with incidence rates of 4 cases per 100,000 population. Infants less than 6 months old still comprise the largest proportion of cases, but adolescents and young adults have accounted for a dramatically increasing share. Reasons postulated for the resurgence of pertussis are varied. The bacteria may have experienced genetic drift in a way that reduced vaccine derived immunity. It is possible that historical prescribing practices may have led to antibiotics given in the early stage of pertussis, thinking they were viral URIs. With the current stress on avoiding antibiotic overuse, physicians may inadvertently allow the full development of the disease. Alternately, the incidence rate increase may be due less to disease factors than an improved reporting system and increase in case detection. Presented is a case of the community response to a pertussis outbreak in Camp Lejeune, NC. From initial detection, to case management, to prevention of further spread, family physicians were an integral part of the public health team that stepped forward. Their interventions aided in preventing this outbreak from detrimentally impacting the operational forces assigned to the base.

3. Case Presentation Index case Laboratory confirmation Outbreak Clinical Case definition Close contact Timeline Symptomatic contacts Close contacts The index case for this outbreak was a fully immunized nine year old girl. She was admitted to a local hospital with cough, mild fever, and inspiratory whoop. There she was cultured and treated for presumed pertussis. A sister who had had similar, though milder symptoms was likewise treated. Of note, the patient went to school for 10 days while sick, and had a sleep over with two friends during that timeframe. The PCR was positive for pertussis four days after the sample was collected. However, due to the fastidious nature of the organism, it wasn�t until 7 days later that the culture had positive growth. By the time this culture was positive, two close friends of the index case had begun to demonstrate pertussis-like symptoms, raising concern for outbreak and spread. The response to this was to enlist the public health and primary care communities in outbreak control. In order to find cases but limit unnecessary cultures, an outbreak clinical case definition for pertussis was developed. A case was defined as anyone with signs or symptoms of pertussis who had been a close contact of the index case or her sister. The term close contact referred to anyone who shared a confined space with a lab confirmed case. Practically speaking, close contacts were those individuals who were in a classroom or school bus with one of the cases. The first day of the confirmed outbreak, the team brought in all contacts who had been identified by the school nurses as having symptoms. At the same time, letters were sent home to students identified as possible close contacts. These letters delineated times when the contacts and their family members would be evaluated. Nearly 900 patients were seen over the next four days. -------------------------------------- The index case for this outbreak of pertussis was a fully immunized nine year old girl. She was admitted to a local hospital with cough, inspiratory whoop, and mild fever. Over the next two days she was cultured and treated for presumed pertussis. The index case�s 11 year old sister had, for two weeks prior, a hacking cough that resolved, and the rest of the family was asymptomatic. There was no history of recent travel. The patient went to school for 7-10 days while sick, and had a sleep over with two friends during that timeframe. Four days after the nasopharyngeal sample was obtained, the confirmatory polymerase chain reaction (PCR) test was positive for pertussis. At the six day point, the state laboratory noted that there was growth on the plate of an �indicator organism� often seen with positive pertussis cultures. 11 days after the culture was drawn there was positive growth of B. pertussis on the media. By the time the final culture was positive, the two close friends of the index case had begun to demonstrate pertussis-like symptoms, raising concern for outbreak and spread. The response to this was to enlist the public health and primary care communities in outbreak control. In order to cast a wide net and limit unnecessary cultures, an outbreak clinical case definition for pertussis was developed. A case was defined as anyone with signs or symptoms of pertussis who had been a close contact of the index case or her sister. The term close contact referred to anyone who had face-to-face contact with a confirmed case, or shared a confined space with a confirmed case for more than an hour. Practically speaking, close contacts were designated as those individuals who shared a classroom or rode the same bus as one of the cases. The public health effort was therefore focused at the two schools attended by the index case and the sister. Upon receiving word that the culture was pertussis positive, an action team was formed to provide contact evaluation. Patients were evaluated and treated using clinical guidelines developed locally in accordance with recommended Centers for Disease Control (CDC) standards to insure a uniform provision of information and care. Patients were asked about their epidemiologic link to the confirmed cases and asked to report active symptoms. The first day, the team brought in all contacts who had been identified by the school nurses as having any symptoms of illness, as well as their families. At the same time, public health and school officials sent letters home to students identified as possible close contacts. These letters delineated times over the next two days when the contacts and their family members would be evaluated. All close contacts and their families were seen over the next four days in school buildings after hours to provide rapid patient flow. This also avoided unnecessary exposures within the hospital. Over these four days nearly 900 patient evaluations were performed. In addition, due to the large number of children placed on social isolation, the base commander in consultation with the public health team closed the base schools on the fifth day after the culture was found to be positive. Although this outbreak occurred on a military installation, only 59 active duty personnel required any intervention that included social isolation. The operational forces, despite the potential for rapid spread in the barracks living arrangements, were unaffected by the outbreak. The index case for this outbreak was a fully immunized nine year old girl. She was admitted to a local hospital with cough, mild fever, and inspiratory whoop. There she was cultured and treated for presumed pertussis. A sister who had had similar, though milder symptoms was likewise treated. Of note, the patient went to school for 10 days while sick, and had a sleep over with two friends during that timeframe. The PCR was positive for pertussis four days after the sample was collected. However, due to the fastidious nature of the organism, it wasn�t until 7 days later that the culture had positive growth. By the time this culture was positive, two close friends of the index case had begun to demonstrate pertussis-like symptoms, raising concern for outbreak and spread. The response to this was to enlist the public health and primary care communities in outbreak control. In order to find cases but limit unnecessary cultures, an outbreak clinical case definition for pertussis was developed. A case was defined as anyone with signs or symptoms of pertussis who had been a close contact of the index case or her sister. The term close contact referred to anyone who shared a confined space with a lab confirmed case. Practically speaking, close contacts were those individuals who were in a classroom or school bus with one of the cases. The first day of the confirmed outbreak, the team brought in all contacts who had been identified by the school nurses as having symptoms. At the same time, letters were sent home to students identified as possible close contacts. These letters delineated times when the contacts and their family members would be evaluated. Nearly 900 patients were seen over the next four days. -------------------------------------- The index case for this outbreak of pertussis was a fully immunized nine year old girl. She was admitted to a local hospital with cough, inspiratory whoop, and mild fever. Over the next two days she was cultured and treated for presumed pertussis. The index case�s 11 year old sister had, for two weeks prior, a hacking cough that resolved, and the rest of the family was asymptomatic. There was no history of recent travel. The patient went to school for 7-10 days while sick, and had a sleep over with two friends during that timeframe. Four days after the nasopharyngeal sample was obtained, the confirmatory polymerase chain reaction (PCR) test was positive for pertussis. At the six day point, the state laboratory noted that there was growth on the plate of an �indicator organism� often seen with positive pertussis cultures. 11 days after the culture was drawn there was positive growth of B. pertussis on the media. By the time the final culture was positive, the two close friends of the index case had begun to demonstrate pertussis-like symptoms, raising concern for outbreak and spread. The response to this was to enlist the public health and primary care communities in outbreak control. In order to cast a wide net and limit unnecessary cultures, an outbreak clinical case definition for pertussis was developed. A case was defined as anyone with signs or symptoms of pertussis who had been a close contact of the index case or her sister. The term close contact referred to anyone who had face-to-face contact with a confirmed case, or shared a confined space with a confirmed case for more than an hour. Practically speaking, close contacts were designated as those individuals who shared a classroom or rode the same bus as one of the cases. The public health effort was therefore focused at the two schools attended by the index case and the sister. Upon receiving word that the culture was pertussis positive, an action team was formed to provide contact evaluation. Patients were evaluated and treated using clinical guidelines developed locally in accordance with recommended Centers for Disease Control (CDC) standards to insure a uniform provision of information and care. Patients were asked about their epidemiologic link to the confirmed cases and asked to report active symptoms. The first day, the team brought in all contacts who had been identified by the school nurses as having any symptoms of illness, as well as their families. At the same time, public health and school officials sent letters home to students identified as possible close contacts. These letters delineated times over the next two days when the contacts and their family members would be evaluated. All close contacts and their families were seen over the next four days in school buildings after hours to provide rapid patient flow. This also avoided unnecessary exposures within the hospital. Over these four days nearly 900 patient evaluations were performed. In addition, due to the large number of children placed on social isolation, the base commander in consultation with the public health team closed the base schools on the fifth day after the culture was found to be positive. Although this outbreak occurred on a military installation, only 59 active duty personnel required any intervention that included social isolation. The operational forces, despite the potential for rapid spread in the barracks living arrangements, were unaffected by the outbreak.

4. Case Presentation Again, if a patient was identified as a close contact and had symptoms associated with pertussis, he was considered a case. These patients were treated with antibiotics and placed in social isolation for five days. Additionally, the patient�s family was given chemoprophylaxis and social isolation. No culture was performed on these presumed cases. If the patient met the criteria of a close contact but was asymptomatic he was given prophylactic antibiotics with social isolation, but his family members were not. If the patient was not a close contact, but had symptoms consistent with pertussis then a culture was performed. Further evaluation would then occur to see if the epidemiologic net needed to be cast wider. -------------------------------------- If the patient was identified as a close contact, and had symptoms associated with pertussis, he or she was considered a case. These patients were treated with antibiotics and placed in social isolation for five days. Additionally, the case�s family was given chemoprophylaxis and five days of social isolation. No culture was performed on these cases. If the patient met the criteria of a close contact but was asymptomatic he or she was given prophylactic antibiotics and five days of social isolation, but the family members were not placed on medication or restricted in any way. If the patient was not a close contact, but had symptoms consistent with pertussis then a culture was performed and treatment given. Further evaluation would then be performed to see if the epidemiologic net needed to be cast wider. Again, if a patient was identified as a close contact and had symptoms associated with pertussis, he was considered a case. These patients were treated with antibiotics and placed in social isolation for five days. Additionally, the patient�s family was given chemoprophylaxis and social isolation. No culture was performed on these presumed cases. If the patient met the criteria of a close contact but was asymptomatic he was given prophylactic antibiotics with social isolation, but his family members were not. If the patient was not a close contact, but had symptoms consistent with pertussis then a culture was performed. Further evaluation would then occur to see if the epidemiologic net needed to be cast wider. -------------------------------------- If the patient was identified as a close contact, and had symptoms associated with pertussis, he or she was considered a case. These patients were treated with antibiotics and placed in social isolation for five days. Additionally, the case�s family was given chemoprophylaxis and five days of social isolation. No culture was performed on these cases. If the patient met the criteria of a close contact but was asymptomatic he or she was given prophylactic antibiotics and five days of social isolation, but the family members were not placed on medication or restricted in any way. If the patient was not a close contact, but had symptoms consistent with pertussis then a culture was performed and treatment given. Further evaluation would then be performed to see if the epidemiologic net needed to be cast wider.

5. Case Presentation No other hospitalizations No further lab confirmed cases Operational impact was minimal In the end, no other individuals were hospitalized, and there were no further laboratory confirmed cases. Although this outbreak occurred on a military installation of 38,000, only 59 active duty personnel required any intervention that included social isolation. The operational forces, despite the potential for rapid spread in the barracks, were unaffected by the outbreak. -------------------------------------- The first day, the team brought in all contacts who had been identified by the school nurses as having any symptoms of illness, as well as their families. At the same time, public health and school officials sent letters home to students identified as possible close contacts. These letters delineated times over the next two days when the contacts and their family members would be evaluated. All close contacts and their families were seen over the next four days in school buildings after hours to provide rapid patient flow. This also avoided unnecessary exposures within the hospital. Over these four days nearly 900 patient evaluations were performed. In addition, due to the large number of children placed on social isolation, the base commander in consultation with the public health team closed the base schools on the fifth day after the culture was found to be positive. Although this outbreak occurred on a military installation, only 59 active duty personnel required any intervention that included social isolation. The operational forces, despite the potential for rapid spread in the barracks living arrangements, were unaffected by the outbreak.In the end, no other individuals were hospitalized, and there were no further laboratory confirmed cases. Although this outbreak occurred on a military installation of 38,000, only 59 active duty personnel required any intervention that included social isolation. The operational forces, despite the potential for rapid spread in the barracks, were unaffected by the outbreak. -------------------------------------- The first day, the team brought in all contacts who had been identified by the school nurses as having any symptoms of illness, as well as their families. At the same time, public health and school officials sent letters home to students identified as possible close contacts. These letters delineated times over the next two days when the contacts and their family members would be evaluated. All close contacts and their families were seen over the next four days in school buildings after hours to provide rapid patient flow. This also avoided unnecessary exposures within the hospital. Over these four days nearly 900 patient evaluations were performed. In addition, due to the large number of children placed on social isolation, the base commander in consultation with the public health team closed the base schools on the fifth day after the culture was found to be positive. Although this outbreak occurred on a military installation, only 59 active duty personnel required any intervention that included social isolation. The operational forces, despite the potential for rapid spread in the barracks living arrangements, were unaffected by the outbreak.

6. Discussion - Investigation Confirm the diagnosis Generate a case definition Confirm the outbreak Inform stakeholders Hypothesize re source and transmission Implement control measures Continue surveillance The heart of this case is the coordination of family physicians and the public health team in investigating the outbreak. The report of the index case to public health authorities set off a series of events that mirrored a general approach to outbreak investigation. It is important to note that these steps occurred in a non-linear manner in order to increase speed and minimize the number of people impacted by the outbreak. The first step in the investigation was confirming the diagnosis. The 11 day culture process was slower than anyone would like. However, it is always essential to ensure an outbreak is genuine before implementing controls. In an outbreak scenario, the CDC�s pertussis case definition is simply an acute cough illness that lasts two weeks. The family physicians and public health team felt that the two week requirement would allow an unacceptable amount of contact between unidentified cases and the uninfected before diagnosis and treatment. It was felt that the case definition previously described would identify infected individuals early in the disease process. The next stage in the outbreak investigation was to confirm that the current disease rates were higher than the baseline. In this particular case, the baseline was that no pertussis cases were endemic to the area. Hence, a single culture proven patient was sufficient to be considered an outbreak. From there, the state and military authorities were informed and educated about the presence of a pertussis outbreak in their jurisdiction. Forming a working hypothesis about the transmission of the pathogen was next. Lack of travel and an easily traceable routine made it simple for investigators to focus on the index case and her close contacts. Contact reporting via clinical interview, bus rosters, and school seating charts provided a clear snapshot of those at highest risk for contracting the disease. Implementation of control measures was the next focus of the public health team and once again brought the family physicians to the fore. Treatment and prophylaxis were some of the tools used in the control of the outbreak. Strategic containment via both the judicious use of social isolation and the closure of the most likely sites of transmission (the schools) were implemented to avert the further spread of pertussis in the community. Continued vigilant surveillance was maintained throughout the incubation period in order to catch any new cases that might emerge from a non-epidemiologically linked source. -------------------------------------- This case is a good example of many basic tenets of field epidemiology. The initiation of an outbreak investigation may occur as a result of something as simple as an observant individual reporting a perceived pattern or increase in a specific disease process. However, in this case, the community surveillance system which mandates required reporting of pertussis automatically brought the index case to the attention of the public health authorities. This set off a series of events that mirrored the general approach to an outbreak investigation that can be found in many sources. It is important to note that these steps occurred in a non-linear manner in order to increase speed and minimize the number of people impacted by the outbreak. The first step in the investigation was confirming the diagnosis. As discussed previously, the pathogen does not lend itself to easy isolation, and the 11 day confirmation process was slower than anyone would like. However, it is always essential to ensure the outbreak is genuine by evaluating all the clinical and laboratory data. After the diagnosis was confirmed, the next step was to generate a case definition. This allows the investigators to distinguish between cases and non-cases as they evaluate the outbreak. The CDC�s clinical case definition for endemic or sporadic pertussis consists of an acute cough illness lasting a minimum of two weeks with paroxysmal cough, inspiratory whooping, or post-tussive emesis. Probable cases meet the clinical case definition, but are not laboratory confirmed or epidemiologically linked to a laboratory confirmed case. Confirmed cases meet both the clinical case definition and have either laboratory confirmation or epidemiologic links to a laboratory confirmed case. In the outbreak scenario, the CDC changes its definition to simply an acute cough illness that lasts two weeks without other symptoms. The low sensitivity and variable specificity of the laboratory findings make the clinical diagnosis far more useful in the outbreak scenario. The physicians and public health team felt that the two week requirement would allow an unacceptable amount of contact between unidentified cases and the uninfected before diagnosis and treatment. Additionally, the epidemiologic links that could be drawn from the index case were limited and clear cut. For these reasons, the working clinical case definition was modified from that proposed by the CDC. The case definition of anyone with signs or symptoms of pertussis who had been a close contact of the index case or her sister was felt to provide a wide net to catch infected individuals early in the disease process. Additionally, it would prevent wasting time (waiting two weeks for cough) and resources (expensive PCR and cultures). Those who had pertussis-like symptoms but were not close contacts would not be considered cases until they met the CDC�s clinical case definition. The goal of these modifications was to give the team with simple rules that could be applied uniformly and yield a reasonably sensitive and specific method of determining cases and non-cases. The next stage in this outbreak investigation was abbreviated compared to many other such inquiries. This step is to confirm the actual presence of an outbreak showing that the current disease rates are higher than the baseline. This is usually done by plotting an epidemiologic curve, which is simply a histogram of cases versus time. The resulting graph can yield important data such as the type of source, time from exposure, and incubation period. In this particular case, the baseline was that no pertussis cases were endemic to the geographic area. Hence, any reported case is above the normal level and two symptomatic patients were sufficient to be considered an outbreak in this region. The next steps happened rapidly and dynamically. The state and military authorities were informed about the presence of a pertussis outbreak in their jurisdiction. Research was conducted to learn the latest information about this disease process. A SF 600 overprint was created to collect demographic, epidemiologic, and clinical data from all the patients that were anticipated. Formulation of a working hypothesis about the source and transmission of the pathogens was the next step. Again, the lack of travel and the easily traceable routine made it easy for investigators to focus on the index case and her close contacts. Contact reporting via a variety of sources (clinical interview, bus rosters, and school seating charts) provided a clear snapshot of those at highest risk for contracting the disease. Implementation of control measures was the next focus of the public health team and once again brought the family physicians to the fore. Treatment and prophylaxis of cases and close contacts were some of the tools used in the control of the outbreak. Strategic containment via both the judicious use of social isolation and the closure of the most likely sites of transmission (the schools) were instrumental in averting the further spread of pertussis in the community. Continued vigilant surveillance was maintained throughout the known incubation period in order to catch any new cases that might emerge from a non-epidemiologically linked source. Communication and education of all interested parties was critical to the successful containment of the outbreak.The heart of this case is the coordination of family physicians and the public health team in investigating the outbreak. The report of the index case to public health authorities set off a series of events that mirrored a general approach to outbreak investigation. It is important to note that these steps occurred in a non-linear manner in order to increase speed and minimize the number of people impacted by the outbreak. The first step in the investigation was confirming the diagnosis. The 11 day culture process was slower than anyone would like. However, it is always essential to ensure an outbreak is genuine before implementing controls. In an outbreak scenario, the CDC�s pertussis case definition is simply an acute cough illness that lasts two weeks. The family physicians and public health team felt that the two week requirement would allow an unacceptable amount of contact between unidentified cases and the uninfected before diagnosis and treatment. It was felt that the case definition previously described would identify infected individuals early in the disease process. The next stage in the outbreak investigation was to confirm that the current disease rates were higher than the baseline. In this particular case, the baseline was that no pertussis cases were endemic to the area. Hence, a single culture proven patient was sufficient to be considered an outbreak. From there, the state and military authorities were informed and educated about the presence of a pertussis outbreak in their jurisdiction. Forming a working hypothesis about the transmission of the pathogen was next. Lack of travel and an easily traceable routine made it simple for investigators to focus on the index case and her close contacts. Contact reporting via clinical interview, bus rosters, and school seating charts provided a clear snapshot of those at highest risk for contracting the disease. Implementation of control measures was the next focus of the public health team and once again brought the family physicians to the fore. Treatment and prophylaxis were some of the tools used in the control of the outbreak. Strategic containment via both the judicious use of social isolation and the closure of the most likely sites of transmission (the schools) were implemented to avert the further spread of pertussis in the community. Continued vigilant surveillance was maintained throughout the incubation period in order to catch any new cases that might emerge from a non-epidemiologically linked source. -------------------------------------- This case is a good example of many basic tenets of field epidemiology. The initiation of an outbreak investigation may occur as a result of something as simple as an observant individual reporting a perceived pattern or increase in a specific disease process. However, in this case, the community surveillance system which mandates required reporting of pertussis automatically brought the index case to the attention of the public health authorities. This set off a series of events that mirrored the general approach to an outbreak investigation that can be found in many sources. It is important to note that these steps occurred in a non-linear manner in order to increase speed and minimize the number of people impacted by the outbreak. The first step in the investigation was confirming the diagnosis. As discussed previously, the pathogen does not lend itself to easy isolation, and the 11 day confirmation process was slower than anyone would like. However, it is always essential to ensure the outbreak is genuine by evaluating all the clinical and laboratory data. After the diagnosis was confirmed, the next step was to generate a case definition. This allows the investigators to distinguish between cases and non-cases as they evaluate the outbreak. The CDC�s clinical case definition for endemic or sporadic pertussis consists of an acute cough illness lasting a minimum of two weeks with paroxysmal cough, inspiratory whooping, or post-tussive emesis. Probable cases meet the clinical case definition, but are not laboratory confirmed or epidemiologically linked to a laboratory confirmed case. Confirmed cases meet both the clinical case definition and have either laboratory confirmation or epidemiologic links to a laboratory confirmed case. In the outbreak scenario, the CDC changes its definition to simply an acute cough illness that lasts two weeks without other symptoms. The low sensitivity and variable specificity of the laboratory findings make the clinical diagnosis far more useful in the outbreak scenario. The physicians and public health team felt that the two week requirement would allow an unacceptable amount of contact between unidentified cases and the uninfected before diagnosis and treatment. Additionally, the epidemiologic links that could be drawn from the index case were limited and clear cut. For these reasons, the working clinical case definition was modified from that proposed by the CDC. The case definition of anyone with signs or symptoms of pertussis who had been a close contact of the index case or her sister was felt to provide a wide net to catch infected individuals early in the disease process. Additionally, it would prevent wasting time (waiting two weeks for cough) and resources (expensive PCR and cultures). Those who had pertussis-like symptoms but were not close contacts would not be considered cases until they met the CDC�s clinical case definition. The goal of these modifications was to give the team with simple rules that could be applied uniformly and yield a reasonably sensitive and specific method of determining cases and non-cases. The next stage in this outbreak investigation was abbreviated compared to many other such inquiries. This step is to confirm the actual presence of an outbreak showing that the current disease rates are higher than the baseline. This is usually done by plotting an epidemiologic curve, which is simply a histogram of cases versus time. The resulting graph can yield important data such as the type of source, time from exposure, and incubation period. In this particular case, the baseline was that no pertussis cases were endemic to the geographic area. Hence, any reported case is above the normal level and two symptomatic patients were sufficient to be considered an outbreak in this region. The next steps happened rapidly and dynamically. The state and military authorities were informed about the presence of a pertussis outbreak in their jurisdiction. Research was conducted to learn the latest information about this disease process. A SF 600 overprint was created to collect demographic, epidemiologic, and clinical data from all the patients that were anticipated. Formulation of a working hypothesis about the source and transmission of the pathogens was the next step. Again, the lack of travel and the easily traceable routine made it easy for investigators to focus on the index case and her close contacts. Contact reporting via a variety of sources (clinical interview, bus rosters, and school seating charts) provided a clear snapshot of those at highest risk for contracting the disease. Implementation of control measures was the next focus of the public health team and once again brought the family physicians to the fore. Treatment and prophylaxis of cases and close contacts were some of the tools used in the control of the outbreak. Strategic containment via both the judicious use of social isolation and the closure of the most likely sites of transmission (the schools) were instrumental in averting the further spread of pertussis in the community. Continued vigilant surveillance was maintained throughout the known incubation period in order to catch any new cases that might emerge from a non-epidemiologically linked source. Communication and education of all interested parties was critical to the successful containment of the outbreak.

7. Discussion � Numbers 88% of those evaluated were either treated or placed on prophylaxis 10 symptomatic individuals were untreated 97% of individuals fully up to date on immunizations 33% of close contacts were symptomatic Next, I�d like to show some statistics that demonstrate interesting aspects of this case. First, 88% of the people evaluated were either treated or placed on chemoprophylaxis. This demonstrates the team�s effectiveness in identifying people at risk for being cases or close contacts. The data also shine a light on areas where the system needs to improve. Of the individuals who had symptoms, 10 were not treated with antibiotics. Four of those could not be epidemiologically linked to the cases so avoiding antibiotics was appropriate. However, the other six individuals should have been placed on treatment or prophylaxis and were not. This emphasizes that education of providers is crucial to ensuring that a consistently high quality of care is given in an outbreak. Finally, one third of the close contacts were symptomatic. This is a particularly notable given that 97% of the individuals evaluated were fully up to date on their pertussis immunizations. Thus, this figure represents the rough approximation of an attack rate for this highly immunized population. While there are certainly inaccuracies inherent to this sort of calculation, this is a real world illustration of just how communicable pertussis is, even in a population where vaccination is routine. -------------------------------------- Although a formal case-control study was not done to confirm the obvious outbreak, the descriptive statistics collected demonstrate a number of interesting aspects of this case. First, 88% of the 898 people evaluated were either treated or placed on chemoprophylaxis. This demonstrates the effectiveness of the school, hospital, and public health officials in identifying people at risk for being cases or close contacts of cases. Also notable is that the impact to the community was essentially kept to the minimum needed to provide adequate containment for the outbreak. The data also shine a light on areas where the system needs to improve. Of the 130 individuals who had symptoms, 10 were not treated with antibiotics. Four of those could not be epidemiologically linked to the cases so avoiding antibiotics was appropriate. However, the other six individuals should have been placed on treatment or prophylaxis and were not. This emphasizes that communication must be ongoing to ensure a consistently high quality level of care is given to all individuals in an outbreak. 33% of the close contacts were symptomatic. This is a particularly important given that 97% of individuals evaluated were fully up to date on their pertussis immunizations per ACIP guidelines. This figure also represents a rough approximation of an attack rate for a highly immunized population. While there are certainly inaccuracies inherent to this sort of calculation, this approximation is a real world illustration of just how communicable pertussis may be, even in a population where vaccination is routine. It certainly lends confirmation for the booster dosing now recommended by the CDC.Next, I�d like to show some statistics that demonstrate interesting aspects of this case. First, 88% of the people evaluated were either treated or placed on chemoprophylaxis. This demonstrates the team�s effectiveness in identifying people at risk for being cases or close contacts. The data also shine a light on areas where the system needs to improve. Of the individuals who had symptoms, 10 were not treated with antibiotics. Four of those could not be epidemiologically linked to the cases so avoiding antibiotics was appropriate. However, the other six individuals should have been placed on treatment or prophylaxis and were not. This emphasizes that education of providers is crucial to ensuring that a consistently high quality of care is given in an outbreak. Finally, one third of the close contacts were symptomatic. This is a particularly notable given that 97% of the individuals evaluated were fully up to date on their pertussis immunizations. Thus, this figure represents the rough approximation of an attack rate for this highly immunized population. While there are certainly inaccuracies inherent to this sort of calculation, this is a real world illustration of just how communicable pertussis is, even in a population where vaccination is routine. -------------------------------------- Although a formal case-control study was not done to confirm the obvious outbreak, the descriptive statistics collected demonstrate a number of interesting aspects of this case. First, 88% of the 898 people evaluated were either treated or placed on chemoprophylaxis. This demonstrates the effectiveness of the school, hospital, and public health officials in identifying people at risk for being cases or close contacts of cases. Also notable is that the impact to the community was essentially kept to the minimum needed to provide adequate containment for the outbreak. The data also shine a light on areas where the system needs to improve. Of the 130 individuals who had symptoms, 10 were not treated with antibiotics. Four of those could not be epidemiologically linked to the cases so avoiding antibiotics was appropriate. However, the other six individuals should have been placed on treatment or prophylaxis and were not. This emphasizes that communication must be ongoing to ensure a consistently high quality level of care is given to all individuals in an outbreak. 33% of the close contacts were symptomatic. This is a particularly important given that 97% of individuals evaluated were fully up to date on their pertussis immunizations per ACIP guidelines. This figure also represents a rough approximation of an attack rate for a highly immunized population. While there are certainly inaccuracies inherent to this sort of calculation, this approximation is a real world illustration of just how communicable pertussis may be, even in a population where vaccination is routine. It certainly lends confirmation for the booster dosing now recommended by the CDC.

8. Conclusion Successful containment of a pertussis outbreak Negligible impact to the operating forces Family physicians and community health leaders as a team Threat of communicable disease epidemic In conclusion, this case demonstrates the successful containment of a pertussis outbreak using basic tenets of field epidemiology. In our environment, we measured success by the minimal impact to the operational forces. From the outset, family physicians joined the community health leaders in their efforts to contain the spread of the disease. They met regularly to discuss ways to control the outbreak, and were on the forefront during the mass evaluations. Their input after each event was used to streamline and improve the follow-on evaluation efforts. From H5N1 influenza to bioterrorist attacks, the threat of a communicable disease epidemic is all too real in today�s world. This outbreak of pertussis served as a real-life test of the Camp Lejeune public health system, and the lessons learned from the response will make the system stronger for the future. -------------------------------------- This case demonstrates the successful containment of a pertussis outbreak using basic epidemiologic principles by physicians and other public health professionals. From the outset, family physicians joined the community health leaders in their efforts to contain the spread of the disease. Epidemiologists, school officials, physicians, health communicators and infectious disease surveillance experts met regularly to discuss ways to control the outbreak. Additionally, family physicians were on the forefront during the mass evaluations. Their input after each event was used to streamline and improve the processes for the follow-on evaluation efforts. From H5N1 influenza to bioterrorist attacks, the threat of a communicable disease epidemic is all too real in today�s world. This outbreak of pertussis served as a real-life test of the Camp Lejeune public health system, and the lessons learned from the response will make the system stronger for the future. In conclusion, this case demonstrates the successful containment of a pertussis outbreak using basic tenets of field epidemiology. In our environment, we measured success by the minimal impact to the operational forces. From the outset, family physicians joined the community health leaders in their efforts to contain the spread of the disease. They met regularly to discuss ways to control the outbreak, and were on the forefront during the mass evaluations. Their input after each event was used to streamline and improve the follow-on evaluation efforts. From H5N1 influenza to bioterrorist attacks, the threat of a communicable disease epidemic is all too real in today�s world. This outbreak of pertussis served as a real-life test of the Camp Lejeune public health system, and the lessons learned from the response will make the system stronger for the future. -------------------------------------- This case demonstrates the successful containment of a pertussis outbreak using basic epidemiologic principles by physicians and other public health professionals. From the outset, family physicians joined the community health leaders in their efforts to contain the spread of the disease. Epidemiologists, school officials, physicians, health communicators and infectious disease surveillance experts met regularly to discuss ways to control the outbreak. Additionally, family physicians were on the forefront during the mass evaluations. Their input after each event was used to streamline and improve the processes for the follow-on evaluation efforts. From H5N1 influenza to bioterrorist attacks, the threat of a communicable disease epidemic is all too real in today�s world. This outbreak of pertussis served as a real-life test of the Camp Lejeune public health system, and the lessons learned from the response will make the system stronger for the future.

9. Questions?

10. Discussion - Pertussis Bordetella pertussis Clinical phases Complications Laboratory findings Medical management Prevention -------------------------------------- Pertussis is a respiratory disease caused by the organism Bordetella pertussis. This aerobic, gram-negative coccobacillus preferentially adheres to ciliated respiratory epithelium where it produces toxins that induce local tissue damage and ciliary paralysis. Loss of ciliary function leads to accumulation of secretions in the airways resulting in paroxysms of involuntary coughing. The gasping inhalations that follow the coughing spells give rise to the common name �whooping cough�. Humans are the exclusive source and vector for the highly communicable illness which is transmitted through respiratory droplets. The incubation period for pertussis ranges from 4-42 days, but most commonly is 7-10 days. Clinically, pertussis has three phases. The initial stage (catarrhal phase) is characterized by typical upper respiratory infection symptoms � profuse rhinorrhea, low-grade fever, mild cough, sneezing, and conjunctival injection. These symptoms last for one to two weeks, and are often indistinguishable from the common cold. The paroxysmal stage follows and last for one to six weeks. It is marked by the classic pertussis symptoms of rapid coughing bursts followed by an inspiratory �whoop� and occasionally post-tussive vomiting. The final stage the convalescent phase. It is typified by the slow resolution of paroxysms over the course of weeks to months, with recurrences common during subsequent upper respiratory infections. Unfortunately, the disease can be difficult to diagnose because there is often an atypical presentation without the classic symptoms. Complications of pertussis are most common in infants and in the elderly. Young patients are at risk for apnea, secondary bacterial pneumonia, and neurologic complications of hypoxia such as encephalopathy and seizure. Older persons may become dehydrated or malnourished due to cough-limited intake of food and fluids. All age groups may have pressure related complications from coughing such as hernia, pneumothorax, rib fracture, epistaxis, or subdural hematoma. Laboratory confirmation of pertussis is complicated by the fastidious nature of the bacteria. Culture of B. pertussis is the current �gold standard� due to an outstanding positive predictive value in the early weeks of the disease. Unfortunately, it requires plating on special media not readily available in all labs. Additionally, the specimen requires either the collection of a nasal aspirate or the use of a polyester swab placed in the posterior nasopharynx for 10 seconds before withdrawal � procedures that are often poorly tolerated by younger patients. The more expensive PCR assay is available in some laboratories, and has the benefits of faster results (one to two days instead of three to seven by culture), an excellent negative predictive value, and superior sensitivity later in the disease course. However, there are concerns about increased false positive rates with this method. Direct fluorescent antibody and serology are other existing tests; however, they have sufficient disadvantages to prevent their recommendation by the CDC. Other non-specific laboratory indicators of pertussis include a normal or slightly elevated lymphocyte predominant white count, and a chest x-ray with a poorly defined heart border and peribronchial thickening. Medical management of pertussis is relatively straightforward. The bacterium demonstrates excellent in vitro susceptibility to beta-lactam antibiotics, fluoroquinolones, macrolides, chloramphenicol, doxycycline, and trimethoprim-sulfamethoxazole (TMP-SMX). Providing antibiotic treatment may decrease the severity of symptoms when started early and limits the spread of infection to susceptible contacts. Erythromycin is the most studied agent, however, the CDC is recommending newer generation macrolides as first line agents due to ease in administration and improved side effect profiles. TMP/SMX is the CDC recommended alternate agent. Cough suppressants, beta-agonists, immunoglobulin, antihistamines, and steroids have not demonstrated benefit in treating pertussis. Prevention of pertussis is accomplished in two ways. Vaccination is the current strategy for primary prevention. Although the immunization has an efficacy of up to 92% in preventing severe disease, its protection is not permanent. The acellular vaccine is available only in conjunction with tetanus and diphtheria toxoids in various formulations. Current ACIP guidelines recommend a primary series of four shots (DTaP) in childhood and the routine use of a booster dose (TDaP) in adolescence or adulthood. Secondary prevention for the spread of disease is with the use of antibiotics among infected individuals and their close contacts. Antibiotic use in those with disease eradicates B. pertussis in the nasopharynx and limits the spread of disease. Antimicrobial prophylaxis in close contacts has only limited evidence in the literature; however, it continues to be recommended. Unlike most prophylactic regimens, pertussis requires a full treatment dose of antibiotics to be given to the contact. -------------------------------------- Pertussis is a respiratory disease caused by the organism Bordetella pertussis. This aerobic, gram-negative coccobacillus preferentially adheres to ciliated respiratory epithelium where it produces toxins that induce local tissue damage and ciliary paralysis. Loss of ciliary function leads to accumulation of secretions in the airways resulting in paroxysms of involuntary coughing. The gasping inhalations that follow the coughing spells give rise to the common name �whooping cough�. Humans are the exclusive source and vector for the highly communicable illness which is transmitted through respiratory droplets. The incubation period for pertussis ranges from 4-42 days, but most commonly is 7-10 days. Clinically, pertussis has three phases. The initial stage (catarrhal phase) is characterized by typical upper respiratory infection symptoms � profuse rhinorrhea, low-grade fever, mild cough, sneezing, and conjunctival injection. These symptoms last for one to two weeks, and are often indistinguishable from the common cold. The paroxysmal stage follows and last for one to six weeks. It is marked by the classic pertussis symptoms of rapid coughing bursts followed by an inspiratory �whoop� and occasionally post-tussive vomiting. The final stage the convalescent phase. It is typified by the slow resolution of paroxysms over the course of weeks to months, with recurrences common during subsequent upper respiratory infections. Unfortunately, the disease can be difficult to diagnose because there is often an atypical presentation without the classic symptoms. Complications of pertussis are most common in infants and in the elderly. Young patients are at risk for apnea, secondary bacterial pneumonia, and neurologic complications of hypoxia such as encephalopathy and seizure. Older persons may become dehydrated or malnourished due to cough-limited intake of food and fluids. All age groups may have pressure related complications from coughing such as hernia, pneumothorax, rib fracture, epistaxis, or subdural hematoma. Laboratory confirmation of pertussis is complicated by the fastidious nature of the bacteria. Culture of B. pertussis is the current �gold standard� due to an outstanding positive predictive value in the early weeks of the disease. Unfortunately, it requires plating on special media not readily available in all labs. Additionally, the specimen requires either the collection of a nasal aspirate or the use of a polyester swab placed in the posterior nasopharynx for 10 seconds before withdrawal � procedures that are often poorly tolerated by younger patients. The more expensive PCR assay is available in some laboratories, and has the benefits of faster results (one to two days instead of three to seven by culture), an excellent negative predictive value, and superior sensitivity later in the disease course. However, there are concerns about increased false positive rates with this method. Direct fluorescent antibody and serology are other existing tests; however, they have sufficient disadvantages to prevent their recommendation by the CDC. Other non-specific laboratory indicators of pertussis include a normal or slightly elevated lymphocyte predominant white count, and a chest x-ray with a poorly defined heart border and peribronchial thickening. Medical management of pertussis is relatively straightforward. The bacterium demonstrates excellent in vitro susceptibility to beta-lactam antibiotics, fluoroquinolones, macrolides, chloramphenicol, doxycycline, and trimethoprim-sulfamethoxazole (TMP-SMX). Providing antibiotic treatment may decrease the severity of symptoms when started early and limits the spread of infection to susceptible contacts. Erythromycin is the most studied agent, however, the CDC is recommending newer generation macrolides as first line agents due to ease in administration and improved side effect profiles. TMP/SMX is the CDC recommended alternate agent. Cough suppressants, beta-agonists, immunoglobulin, antihistamines, and steroids have not demonstrated benefit in treating pertussis. Prevention of pertussis is accomplished in two ways. Vaccination is the current strategy for primary prevention. Although the immunization has an efficacy of up to 92% in preventing severe disease, its protection is not permanent. The acellular vaccine is available only in conjunction with tetanus and diphtheria toxoids in various formulations. Current ACIP guidelines recommend a primary series of four shots (DTaP) in childhood and the routine use of a booster dose (TDaP) in adolescence or adulthood. Secondary prevention for the spread of disease is with the use of antibiotics among infected individuals and their close contacts. Antibiotic use in those with disease eradicates B. pertussis in the nasopharynx and limits the spread of disease. Antimicrobial prophylaxis in close contacts has only limited evidence in the literature; however, it continues to be recommended. Unlike most prophylactic regimens, pertussis requires a full treatment dose of antibiotics to be given to the contact.