Biological agents

Chapter 2.3JF Gehanno, M.D., Ph.D.

University of Rouen

Biological hazards

• Non infectious effects– Toxic effects :• Part of the membranes of bacteria (Endotoxins)• Toxins produced by moulds (mycotoxins)

– Allergy• Infectious effects– Bacteria, fungi, viruses …– We will focus on infection …

European Classification of biological agents (based only on the risk of infection)

Group Can cause human disease

Can be a hazard for workers

Can spread to the

community

Effective prophylaxis or

treatment available1 No - - -

2 Yes Yes Unlikely Yes

3 Yes Yes Possible Yes

4 Yes Yes High risk No

Hazardous agents are those belonging to group 2, 3 and 4Exemples :Group 2 : Clostridium perfringens, CytomegalovirusGroup 3 : Mycobacterium tuberculosis, Hepatitis B virus, Plasmodium falciparumGroup 4 : Lassa virus, Ebola virus

Sources of exposure

• Patients in hospital settings• Bugs (ticks, sarcoptes …)• Animals (veterinarians, slaughterhouses)

The way to infection

Emission of germs AerialContact – ingestionPercutaneous

Infection if susceptible

Reservoir

HostDispersion infection

Main occupations exposed

• Healthcare workers (many viruses)– hazards represented by biological agents present

in patients• Farmers (brucellosis, zoonosis)• Outdoor workers (Leptospirosis, lyme disease)

Some biological agents

Hepatitis A

• Spread in the feces of infected individuals– Risk for travellers in low income countries

• Risk of spreading to the community by infected food handlers

Hepatitis B

• A high risk for healthcare workers (HCWs)• Blood exposure– Needlestick exposures for HCWs• Up to 45% of risk to be infected in case of needlestick

exposure with a needle that have been used for an infected patient

– Skin contact (rescuers)– Wounds (police officers, fire fighters)

Tuberculosis• Occupational risk for– HCWs– People working with migrants from high

prevalence countries• Transmition by small dropplets released by

infected patients– Dropplets too small to settle– Can spread at several meters from the patient

Prevention

Risk assessment

• Identify the sources of biological agents• Identify the possible ways of transmission• Identify susceptible workers

Avoid exposure

Isolation of patient

Reservoir

HostDispersion

Avoid exposure

Reservoir HostDispersion

Barriers

GlovesMasks

Long sleeves for outdoor workers

Which mask for HCWs ?• Big dropplets (pertussis, meningococcal

infection, influenza …)– Settle at short distance (1m) & straight trajectory– Surgical mask enough

• Small dropplets (tuberculosis, chickenpox …)– Don’t settle (airborne transmission)– Respirator needed (N95 or FFP2)

Avoid contamination

Reservoir HostDispersion

Hand washing

Standard precautionsDesinfection of surfaces

Early removal of ticks

Vaccination

Hepatitis B vaccine for HCWsHepatitis A vaccine for sewage workersLeptospirosis vaccine for foresters

Reservoir HostDispersion

Avoid infection

Chemoprophylaxis for HIV in case of needlestick exposureAntibioprophylaxis in case of exposure to Bordetella pertussis

Reservoir

HostDispersion infection

Preventive treatment

Treat infection

Antibiotics in case of erythema migrans skin lesion following tick bite

Reservoir

HostDispersion infection

Early treatment

Treat infection

Reservoir

HostDispersion infection

Follow upScreaning

And in any case …

• INFORMATION OF THE WORKER ABOUT THE RISKS AND THEIR PREVENTION

Don’t forget the WARP

• Work : could the work of the patient be (part of) the cause or the aggravation of his/her complaint or disease? • Skin lesion for a sewage worker

• Activities : could the complaint / disease of the patient have consequences for his/her activities and participation in work• Hepatitis B infection in a surgeon• Tuberculosis in an HCW

• Referral : should I refer my patient to an occupational physician or another specialist • Should this pregnant HCW, unprotected against rubella, take specific

precautions ?• Prevention : Can I do something to prevent the (return of the) complaint or

disease?• Is this HCW protected against hepatitis B ?

Some useful links• Siegel JD, Rhinehart E, Jackson M, Chiarello L, and the Healthcare Infection

Control Practices Advisory Committee, 2007 Guideline for Isolation Precautions: Preventing Transmission of Ifnectious Agents in Healthcare Settings, June 2007 – http://www.cdc.gov/ncidod/dhqp/pdf/isolation2007.pdf

• Canadian Centre for Occupational Health and Safety. Biological Hazards. http://www.ccohs.ca/oshanswers/biol_hazards/

• National Institute for Occupational Safety and Health (NIOSH). Health Care Workers. http://www.cdc.gov/niosh/topics/healthcare/

• National Institute for Occupational Safety and Health (NIOSH). Diseases & Injuries. http://www.cdc.gov/niosh/topics/diseases.html