Biological agents
Chapter 2.3
JF 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 available
1
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 4
Exemples :
Group 2 : Clostridium perfringens, Cytomegalovirus
Group 3 : Mycobacterium tuberculosis, Hepatitis B virus, Plasmodium falciparum
Group 4 : Lassa virus, Ebola virus
Sources of exposure
• Patients in hospital settings
• Bugs (ticks, sarcoptes …)
• Animals (veterinarians, slaughterhouses)
The way to infection
Reservoir
Emission of germs
Dispersion
Aerial
Contact – ingestion
Percutaneous
Host
infection
Infection if susceptible
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
Reservoir
Isolation of patient
Dispersion
Host
Avoid exposure
Barriers
Reservoir
Dispersion
Host
Gloves
Masks
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
Hand washing
Reservoir
Dispersion
Host
Standard precautions
Desinfection of surfaces
Early removal of ticks
Vaccination
Reservoir
Dispersion
Host
Hepatitis B vaccine for HCWs
Hepatitis A vaccine for sewage
workers
Leptospirosis vaccine for foresters
Avoid infection
Preventive treatment
Reservoir
Dispersion
Host
infection
Chemoprophylaxis for HIV
in case of needlestick
exposure
Antibioprophylaxis in case
of exposure to Bordetella
pertussis
Treat infection
Early treatment
Reservoir
Dispersion
Host
infection
Antibiotics in case of
erythema migrans
skin lesion following
tick bite
Treat infection
Follow up
Screaning
Reservoir
Dispersion
Host
infection
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