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Occupational Infections. By M.H.Davari MD. Occupational Infections. Occupational infections are human diseases caused by work-associated exposure to microbial agents. Occupational and non-occupational infections are the same, except: identification of the source of exposure

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Occupational infections

Occupational Infections

By M.H.Davari MD


Occupational infections1
Occupational Infections

  • Occupational infections are human diseases caused by work-associated exposure to microbial agents.

  • Occupational and non-occupational infections are the same, except:

    • identification of the source of exposure

    • epidemiologic control

    • prevention.


TUBERCULOSIS

  • Transmission: Airborne

  • The bacilli may lead to:

    • latent tuberculosis infection (LTBI)

    • tuberculosis disease (TB)

  • Staffs of laboratories and necropsy rooms are 100 and 200 times more likely than the general public to developtuberculosis.

  • Other high-prevalence work environments: hospitals, longtermcare facilities, and dialysiscenters


  • Bacilli exists in: gastric fluid, CSF, urine, sputum, and tissue specimens harboring active lesions.

  • TB may be activated at any time, and cause acute pulmonary or systemic disease.

  • The incubation period is 4-12 weeks, and infection usually remains subclinical without active disease, but PPD is positive.

  • PPD: Purified protein derivation


1 ppd
1. PPD

  • Occupational periodic PPD in:

    • Contact with infected patients

    • contact with infected primates or cattle (e.g., veterinarians, zoo keepers, primate handlers)


Positive ppd
Positive PPD:

  • 5mm is (+) in:

    • Close contacts of infectious patients

    • immunosuppressed patients:

      • organ recipients

      • known or suspected HIV infection.

  • 10mmis (+) in:

    • high-risk occupational groups

    • immigrants from high prevalence areas

    • Alcoholics

    • IV Drug abusers

  • No risk factors and low prevalence: 15 mm or more.

  • PPD may be negative in: measles, Hodgkin disease, sarcoidosis, or immunosuppressive states.


  • Prophylaxis in a positive PPD:

    • Newly infected, including recent converters (within 2 years)

    • Household contacts of active cases

    • Abnormal CXR consistent with TB (or prior active disease), with inadequate past therapy

    • Persons whose reactivation may have public health consequences (e.g., school teachers).

    • AIDS or HIV+.

    • Silicosis

    • IDDM

    • Hematologic or reticuloendothelialcancer

    • Chronic undernutrition

    • Ileal bypass

    • Renal failure requiring dialysis

    • History of prolonged immunosuppressive therapy, as well as IDUs.

    • All reactors younger than 35 years of age


  • Before starting prophylaxis, a CXR is taken on all skin test reactors. Any abnormalities should be thoroughly evaluated for active disease.

  • There are 4 accepted regimens, Each has:

    • initial 2 months phase

    • followed by continuation phase of 4 or 7 months.

  • Isoniazid and Rifampicin are the 2 most powerful anti-TB drugs included in the regimen in most circumstances.

  • In Person that prophylactic AB is contraindicated: serial CXR


2 quantiferon tb
2. QuantiFERON-TB

  • Recently, the QuantiFERON-TB Gold test has been approved for use instead of PPD, for diagnosing both LTBI and TB infections.

  • uses freshly heparinized whole blood to detect interferon-y from individuals sensitized to tuberculin proteins.

  • more sensitive

  • equally specific

  • needs only one visit and is easier than PPD.


  • Persons with known contact with a patient and unknown PPD status should be PPD tested immediately, and then after 8-12 weeks.

  • If conversion occurs, physical examination and CXR are needed.


Hepatitis b
HEPATITIS B

  • most frequent (10 times) among health care, laboratory, and public safety workers (before vaccine).

  • Fulminant hepatitis

  • Chronic carrier states

    • Cirrhosis & Liver cancer

  • The virus exists in: Blood, CSF, synovial, pleural, peritoneal, pericardial, amniotic fluids, semen and vaginal secretions.

  • Viral titers in urine, feces, tears, and saliva are low.

  • IV drug abuse is most important transmission

  • Sexual and maternal-child transmissions are alternative modes of transmission.


    • Needlestick: 30% transmission.

    • HBV: 1 month on dried surfaces.

    • Pre placement :

      • HBS Ag. HBS Ab. HCV Ab

    • The usual schedule for vaccination: 0, 1, and 6 months.

    • High-risk workers in some countries: Accelerated schedule at 0, 1, and 3 weeks and a final 12 months dose.


    • Vaccine Protection:

      • At birth: Highly protective

      • 40 y/o: 90%

      • 60 y/o: 75%

    • Those who developantibodies,lose them over time, although they remain protected.

    • We should check for HBsAb 4 weeks to 6 months after primary series.

    • If HBsAb is negative:

      • 1 additional dose: 15-25% Ab Protection

      • 3 additional doses (totally 6 doses): 30-50% Ab Protection


    • No Abafter 6 total doses: Changing positions at work not involving blood or blood products.

    • Position change not possible: Vaccination with MerckRecombivax HB for hemodialysis patients or 2 doses of the Engerix-B vaccine.

    • More than 6 months past vaccination and HBsAb(-)  One additional dose of vaccine


    Hepatitis c
    HEPATITIS C

    • Routes of transmission: Blood transfusion, IV drug use, sexual or household exposures, and sometimes, bloodborne pathogen transmission.

    • Needlestick: 1.8%

    • Diagnosis:

      • (EIA): 97% sensitivity within 6-8 weeks of exposure

      • Positive EIA tests: Confirmatory testing with highly sensitive RT-PCR assays for HCV RNA.

      • RIBA (recombinant immunoblot assay): If EIA was pos. and RT-PCR was neg.

    • Chronic carriers recently treated:

      • parenteral peg-interferon-alfa

      • combined with oral ribavirin.


    • Exposure to knowenHCV positive blood:

    • Test HCV RNA 2-4 week later

    • Post exposure prophylaxy(some study)


    HIV

    • Occupational HIV transmission have declined:

      • Antiretroviral agents in HIV Pos. patients

      • Post exposure prophylaxy (PEP)

    • PEP:

      • To reduce drug toxicity  used only in high-risk injuries.

      • Multiple drugs are used when:

        • Injuries involve larger amounts of blood (large-bore needles, deep punctures, and visible blood on devices, needles used in patients' arteries or veins).

        • When higher concentrations of virus are suspected (e.g., AIDS patients, acute seroconversions, high viral loads, and concentrated virus in special laboratory situations).


    • If the source is unknown or has an unknown HIVstatus, PEP generally is not warranted.

    • If the source is known case:

      • HIV PEP usually constitutes a 4-week course of treatment, and we should monitor for side effects in this period, specially the first 3 days.

      • HIV tests: Baseline, 6 weeks, 3 months, and 6 months. Also 12 months if the source is coinfected with HIV and HCV, or the individual is HCV positive.


    Travel
    Travel

    • Some lllnesses contracted during travel are specific to the destination, such as malaria or hepatitis A.

    • Few vaccinations are currently required for entry into some countries.

    • There is the larger number of vaccine-preventable diseases for which vaccinations are not required.


    Hepatitis a
    Hepatitis A

    • Presentation:

      • Younger than 6 yr: asymptomatic

      • Adults: fever, malease, juandice(lost 27 work day)

  • Vaccination prior to travel to Mexico, the Caribbean, and all the other countries where food and water are less than optimal is important.

    1. The vaccine is both safe and effective, protection rates of 80-96%by 2 weeks and almost 100% protection by week 4.

  • Second dose: 6-12 months after the first, which provides long-term protection.

    2. IG:less protective, Hepatitis A

    • where vaccination is contraindicated

    • where travel is imminent,


  • Rabies
    Rabies

    • Rabies poses a hazard in countries where animals are not vaccinated routinely and where dogs are the most frequent hazard.

    • Young children, hikers, and long-term travelers are the groups where pre-exposure vaccination should be considered.

    • The 3-dosepre-exposure vaccination series is administered at 0, 7, and 21-28 days.

    • Post exposure: IG + vaccine (5 dose)


    Meningococcal disease
    Meningococcal Disease

    • Meningococcal meningitis and bacteremia caused by Neisseria meningitidis is endemic in parts of subSaharan Africa during the dry season.

    • Vaccination for travelers with close contact with local population is recommended and required for those traveling to Saudi Arabia for the Hajj.

    • 2 vaccines are used in US. The older polysaccharide vaccine protects for only 3 years. The newer conjugate vaccine provides longer immunity and is used currently for adolescents.


    Malaria

    • Those from nonendemic countries :

      • severe illness

      • developing symptoms many months after returning from malarious regions.

    • 4 types of malaria: Plasmodium falciparum, P. vivax, P. ovale, and P. malariae.

    • P. falciparumis the most serious form and has developed resistance in many areas of the world.


    Recommended travel vaccinations
    RECOMMENDED TRAVEL VACCINATIONS

    Malaria

    • nonresistant areas for P. falciparum (generally in Central America and the Middle East):

      • chloroquine or hydroxychloroquine can be used.

      • Chloroquine is taken weekly beginning1 week before entering, weekly during travel, and for 4 weeks after leaving the malarious area.

    • If chloroquineresistance exists (Southeast Asia, India, Africa, and South America), other forms of malaria prophylaxis :

      • mefloquine, doxycycline, and atovaquone-proguanil.


    Recommended travel vaccinations1
    RECOMMENDED TRAVEL VACCINATIONS

    Malaria

    • Mefloquine :

      • associated with bad dreams, anxiety, depression, psychosis, a lowered seizure threshold, and cardiac conduction abnormalities.

      • This drug is taken once a week in a schedule similar to chloroquine.

    • Doxycycline:

      • photosensitivity, gastrointestinal disorders, rash, and diarrhea.

      • This is taken once a day, 1-2 days before enteringand dailycontinuingup to 4 weeks after leaving the malarious area.


    Recommended travel vaccinations2
    RECOMMENDED TRAVEL VACCINATIONS

    Malaria

    • Atovaquone-proguanil :

      • newest agent with few adverse effects that include abdominal pain, nausea, vomiting, diarrhea, headache, elevated transaminases, and pruritus.

      • Usage: Daily, 1 day before entering and continuing up to 7 days after leaving the malarious region.

    • Reduce mosquito bites: Use of an effective DEET-containing repellent on exposed skin (avoiding the eyes and mouth), mosquito netting, treatment of clothing and mosquito netting with permethrin, and avoidance of outdoor activity during the evening hours.


    Traveler's Diarrhea (TD)

    • Traveler's diarrhea (TD)’s a common problem for travel to areas with less than optimal food and sanitation.

    • Affects up to 30-70% of travelers during the first 2 weeks of travel.

    • Causes:

      • Noninfectious: Jet lag and changes in diet

      • Infections: (ETEC), Campylobacter, Salmonella, Shigella, enteroaggregative E. coli, and other bacterias, and viruses like norovirus and rotavirus.


    Recommended travel vaccinations3
    RECOMMENDED TRAVEL VACCINATIONS

    Traveler's Diarrhea (TD)

    • Treatment :

      • uncomplicated:single dose of 750-1000 mg from quinolone for diarrhea

      • more severe forms: 3-day course for or rifaximin (200mgtidfor3 days).

    • Because of quinolone-resistant Campylobacter in Thailand and India, use of azithromycin as a backup should be considered.


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