Alameda County Influenza Update Rosilyn Ryals, M.D. Division of Communicable Disease Control & Prevention Alameda County Public Health Department November 2005
Outline • Influenza • The Pandemic Threat
What is Influenza? • Contagious, acute, febrile, respiratory illness caused by viruses • Epidemics of influenza occur during winter months in temperate regions, like the U.S. • Every year in the United states: • 5 to 20% of the population get flu • >200,000 people are hospitalized from flu complications • Approximately 36,000 people die from flu (primarily high risk persons)
High Risk Population • Adults >65 years • Children 6-23 months • Persons aged 2-64 yrs. with chronic lung, heart or metabolic disorders:- heart disease (ever diagnosed) - asthma (taking medication)- diabetes (ever diagnosed) • Persons with hemoglobinopathies or immunosuppression • Children and adolescents on long-term aspirin therapy • Women pregnant during influenza season
High Risk Population (continued) • Adults and children who have any condition that can compromise respiratory function. • Residents of nursing homes and other chronic-care facilities Plus those in close contact with high risk persons: • Household members and out-of-home care givers of infants under the age of 6 mos. • Healthcare workers who provide direct, hands-on care to patients - ambulatory health care services- hospitals- nursing and residential care facilities
High Risk Group Impact on Alameda County • Alameda County has a population of about 1.5 million people • The high risk groups identified comprise approximately 1/3 of the county population
Symptoms of Influenza • Fever • Headache • Malaise • Cough • Sore Throat • Runny or stuffy nose • Myalgia • GI symptoms (nausea, vomiting, and diarrhea) – primarily in children
Influenza-Course • Incubation: 1-4 days, averagely 2 days • Adults can be infectious from the day before symptoms until about 5 days after onset • Children may be infectious > 10 days • Severely immunocompromised persons may shed virus for weeks or months • Uncomplicated influenza illness typically resolves in 3-7 days
Influenza- Complications • Pneumonia – usually secondary bacterial • Dehydration • Exacerbation of chronic conditions • Sinus and ear infections (children) • Febrile seizures in children
Biology of Influenza • Influenza viruses belong to the family Orthomyxoviridae • There are 3 distinct types of influenza: A, B and C • Influenza A and B are the two types that cause epidemic human disease • Influenza A is further categorized into subtypes on the basis of two surface antigens: hemagglutinin (H) and neuraminidase (N) • Type A Influenza has 16 different Hs and 9 different Ns • Human disease with Influenza A has historically been caused by three subtypes of H (H1, H2, and H3) and two subtypes of N (N1 and N2)
Biology of Influenza (continued) • All known subtypes of influenza A can be found in birds • Influenza B viruses are not categorized into subtypes. • Standard nomenclature for influenza viruses includes: (1) Influenza type, (2) Place of initial isolation, (3) Strain designation, and (4) Year of isolation, and (5) H and N subtypes for Influenza A. For example, influenza A isolated in a California patient in 2004 would be written as: A/California/7/2004 (H3N2)
Biology of Influenza (continued) • Influenza A viruses are the most worrisome of all the well-established infectious diseases: • Mutate rapidly • In addition to humans, they infect pigs, horses, sea mammals, and birds • They have a large number of subtypes maintained in aquatic birds, providing a perpetual source of viruses and a huge pool of genetic diversity
Biology of Influenza (continued) • Influenza A viruses are described as “sloppy, capricious, and promiscuous” because: • They lack a proof-reading mechanism to detect and correct small errors that occur when the viruses copy themselves. • This allows for constant stepwise changes in their genetic makeup termed antigenic drift • Though small, these slight variations keep populations susceptible to infection (This explains need for a new vaccine for each winter season)
Biology of Influenza (continued) • The genetic content of influenza viruses is segmented into 8 genes • This facilitates the swapping of gene segments during co-infection with hman and avian influenza viruses, thereby creating a new virus subtype that will be entirely or largely unfamiliar to the human immune system. • If this “novel strain” contains a mix of genes causing: severe disease and allowing easy human-to-human transmission, a pandemic is ignited. This is termed: antigenic shift.
Biology of Influenza (continued) • Usually a single strain of influenza virus prevails during an epidemic • Occasionally, two different strains within a single subtype (e.g. A/Victoria/3/75 (H3N2)or A/Texas/1/77 (H3N2) or two different influenza A subtypes (H1N1 and H3N2) may circulate simultaneously.
InfluenzaTransmission • Primarily transmitted person-to-person by large virus-laden droplets (as generated by cough or sneezing within 3 feet of susceptible person) • Direct or indirect contact with virus-laden respiratory secretions followed by touching the eyes, nose or mouth of a susceptible person
Laboratory Diagnosis • It is difficult to diagnose based on clinical symptoms alone. Similar symptoms can be caused by other illnesses, e.g. • Mycoplasma peumoniae • Adenovirus • Respiratory Syncytial Virus • Rhinovirus • Parainfluenza Viruses • Legionella
Laboratory Diagnosis TEST Time for Results • Viral culture* 3-10 days • Serology >2 weeks • Rapid antigen testing: <30 minutes • PCR 1-2 days • Immunofluorescence assays 2-4 hours *Only culture isolates can provide specific information: circulating strains and subtypes
Prevention of InfluenzaInter-pandemic Period VACCINATION
Inactivated Influenza Vaccine • Influenza vaccine can be given to people 6 months of age and older. It is recommended for people who are at risk of serious influenza or its complications, and for people who can spread influenza to those at high risk (including all household members)
Live Attenuated Influenza Vaccine Live, attenuated influenza vaccine (L.A.I.V.) was licensed in 2003. L.A.I.V. contains live but attenuated (weakened) influenza virus. It is sprayed into the nostrils rather than injected into the muscle. It is recommended for healthy children and adults from 5 through 49 years of age, who are not pregnant. Recipients may shed virus.
Influenza Vaccination • Influenza viruses are constantly changing. Therefore, influenza vaccines are updated every year, and annual vaccination is recommended. • For most people influenza vaccine prevents serious illness caused by the influenza virus. It will not prevent “influenza-like” illnesses caused by other viruses. • It takes about 2 weeks for protection to develop after vaccination, and protection can last up to a year.
2005-2006 Influenza Vaccine • Inactivated Influenza Vaccine • A/New Caledonia/20/99 (H1N1) • A/New York/55/2004 (H3N2) • B/Jiangsu/10/2003 • Live attenuated Influenza Vaccine (LAIV) • A/New Caledonia/20/99 (H1N1) • A/California/7/2004 (H3N2) • B/Jiangstu/10/2003
Pneumococcal Vaccination • There are two licensed vaccines: (1) Pneumococcal Conjugate Vaccine, and (2) Pneumococcal Polysaccharide Vaccine. • Recommendations for Pneumococcal Vaccine include population at high risk for influenza and its complications.
Prevention of Influenza Antivirals
Antiviral therapy and prophylaxis Adamantine Derivatives: (1) Amantadine (2) Rimantadine Neuraminidase Inhibitors: (1) Zanamivir (2) Oseltamivir (Tamiflu)
Antivirals for Treatment • Any person with life-threatening influenza-related illness • Any person at high-risk for serious complications of influenza and who is within the first 2 days of illness onset
Antivirals for Prophylaxis • All persons who live or work in institutions caring for people at high risk of complications from influenza should be given antiviral medication in the event of an institutional outbreak • Persons at high risk of serious influenza complications should be given antivirals if they are likely to be exposed to others infected with influenza.
Impacts of Antiviral Drug Therapy • Adamantanes • Reduce duration of illness (1 day) • No studies on severity or complications • Oseltamivir (neuraminidase inhibitors) • Reduce duration of illness • Pooled analysis of randomized controlled trials* • Decreased hospitalization by 59% (p = .02) • Decreased lower resp tract illness by 55% (p <.001) • Decreased antibiotic use by 27% (P <.001) *Kaiser, Arch Intern Med 2003
Prevention of Influenza Infection Control
Infection Control • Encourage annual Influenza vaccine for Health Care workers • Use of Standard Precautions: (1) Handwashing (2) Gloves (3) Mask, Eye Protection, Face Shield: when patient care activities are likely to generate splashes or sprays (4) Gown: protect skin and prevent soiling of clothing in patient care activities that are likely to generate splashes or sprays (5) Patient-Care Equipment (6) Environmental Control (7) Linen (8) Occupational Health and Bloodborne Pathogens (9) Patient Placement: private room or cohorting
Infection Control • Droplet Precautions: (1) Patient Placement: Private room; cohort; or maintain at least 3 feet spatial separation (2) Mask: as per Standard precautions and when working within 3 feet of an infected patient (3) Patient transport: limit to essential purposes only; minimize dispersal of droplets by masking patient, if possible.
Infection Control • Contact Precautions: (1) Patient Placement (2) Gloves and handwashing (3) Gown (4) Patient transport (5) Patient-Care Equipment
Infection Control • Airborne Precautions (smaller particles than respiratory droplets); may result from procedures like endotracheal intubation, suctioning, nebulizer treatment, or bronchoscopy. These procedures can result in dissemination of airborne droplets over long distances; requires use of special air-handling and ventillation.
Infection Control • Airborne Precautions (continued): (1) Patient placement: negative air pressure with 6-12 air exchanges per hour, and appropriate discharge of air outdoors; keep door closed; can also cohort if private room not available. (2) Respiratory protection: wear an N95 respirator when entering room (3) Limit movement and transport of patient to essential purposes If transport or movement is necessary, use mask for patient, if possible.
Infection Control In Doctor’s Offices and Clinics, in addition to standard precautions and annual influenza immunization of health care workers: • Encourage patients with respiratory and other symptoms consistent with influenza to call in advance of coming in. • Encourage the use of masks by symptomatic patients or the use of tissues to cover coughs/sneezes
Goals of Influenza Surveillance in the U.S. • Find out when and where influenza activity is occurring • Determine what type of influenza viruses are circulating • Detect changes in the influenza viruses • Track influenza-related illness • Measure the impact influenza is having on deaths in the U.S.
U.S. Influenza Surveillance System • 75 WHO and 50 NREVSS Collaborating Labs throughout U.S. report: # specimens tested, # positive for influenza A or B • U.S. Influenza Sentinel Providers Network: 1000 providers around the country report number of persons seen, and number with influenza-like illness by age group • 122 Cities Mortality Reporting systems report # of pneumonia or influenza deaths • State and Territorial Epidemiologists report the level of influenza activity in the state • Influenza-associated pediatric mortality report lab-confirmed influenza deaths in children <18 years old
U.S. Influenza Surveillance System(continued) (6) Emerging Infections Program conducts surveillance for lab-confirmed influenza-related hospitalizations in persons less than 18 years of age in 57 counties throughout U.S. (covering 10 states) (7) New Vaccine Surveillance Network provides population-based estimates of lab-confirmed influenza hospitalization rates for children <5 years who live in 3 U.S. counties(Ohio, Tennessee, and New York)
Pandemic Influenza • Worldwide outbreak of a novel strain • Associated with high morbidity, excess mortality, and social and economic disruption • First recorded pandemic that fits influenza profile occurred in 1580
Pandemic Influenza in the 20th Century • 1918-19 Spanish Flu (H1N1) • 20-50 million deaths worldwide • >500,000 U.S. deaths • 1957-58 Asian Flu (H2N2) • 70,000 U.S. deaths • 1968-69 Hong Kong Flu (H3N2) • 50,000 U.S. deaths
Avian H5N1 in Asia • Continuing presence in Asia since 1996 • Documented direct avian to human transmission, Hong Kong,1997 • Enzootic and epizootic of unprecedented size and complexity • 9 countries with ongoing outbreaks (most recently in Malaysia) • Ongoing human cases with high case fatality, mostly in healthy children and young adults • Ongoing evolution of the virus’ antigenic, genetic and functional properties • No sustained human to human transmission to date
Why are We Concerned? • Increasing countries/areas with avian influenza • Uncertainties on progress of control • Ongoing human infection with avian H5N1 • Limited implementation of protective measures • Co-Circulating human influenza viruses • Risk of genetic reassortment leading to pandemic strain • Majority of human population would have no immunity • H5N1 resembles the 1918-19 pandemic influenza in that healthy young persons are affected and a deadly feature is a primary viral pneumonia.
Human Infections • H5N1 - severe • 1997 Hong Kong: 18 cases; 6 deaths • 2003 Hong Kong: 2 cases; 1 death • 2004 Vietnam and Thailand: 40 cases; 29 deaths • 2005 Hunan (China): 3 cases, 2 deaths • H9N2 - mild • 1999 Hong Kong: 2 cases (mild) • 2003 Hong Kong: 1 case (mild)
17 Human Cases 12 Deaths 94 Human Cases 42 Deaths 4 Human Cases 4 Deaths 4 Human case 3 Deaths CIDRAP, 8/2005
Influenza H5N1: expanded host range? • Domestic poultry • Wild birds • infected • reservoir • Humans • Swine (China) • Cats? (Netherlands) The natural hosts of the influenza A virus