Most of the information in
this document was taken from the CDC West Nile Virus Home Page (http://www.cdc.gov/ncidod/dvbid/westnile).
WNV Infection in Humans
The most likely route of WNV
infection to humans is through the bite of an infected mosquito. Most cases of
WNV are probably not acquired in the workplace but there are some workers at risk
of WNV infection, such as people who work outside. Workers who perform necropsies of infected
birds or handle WNV-infected tissues or fluids are also at risk of WNV
infection if skin penetration or laceration occurs. There is no evidence that a person can get
the virus from handling live or dead infected birds (CDC). WNV may also be
transmitted by organ transplantation, blood transfusion, or possibly breast
milk [CDC 2002a,b].
Laboratory-acquired infection has also been documented [CDC 2002d].
Most human WNV infections
cause either no symptoms or a mild flu-like illness. The most severely affected
patients may develop an inflammation of the brain, or
the membranes of the brain or spinal cord, or both, called encephalitis,
meningitis, or meningoencephalitis, respectively.
These severe cases may be fatal. Persons over age 50 are at higher risk of
severe illness following infection. All
workers should be careful to follow the recommendations listed below even
though older workers may be at higher risk of severe disease. Recovery can take up to a year. Students with
immuno-deficiencies should not handle animals at any
time.
What are the signs and symptoms of WNV infection in
humans?
Most human WNV infections
cause either no symptoms or a mild flu-like illness. Mild symptoms include
fever, fatigue, headache, and muscle or joint pain. Signs of severe infection
include high fever, stiff neck, disorientation, tremors, muscle weakness, and
paralysis. The most severely affected patients may develop an inflammation of
the brain, or the membranes of the brain or spinal
cord, or both, called encephalitis, meningitis, or meningoencephalitis,
respectively. The incidence of severe disease is highest among persons over age
50. These severe cases may be fatal. The time of incubation from mosquito bite
to clinical symptoms is reported to be from 3 to 14 days.
Is a woman's pregnancy at risk if she is infected with
WNV?
There is one documented case
of transplacental (mother-to-fetus) transmission of
WNV in humans (CDC 2002c). . The newborn
in this case was infected with WNV at birth and had severe medical problems. It
is unknown whether the WNV infection itself caused these problems. More
research is needed to understand the possible effects of WNV on pregnancy. Pregnant women should take precautions to
reduce their risk for WNV infection by avoiding mosquitoes, wearing protective
clothing and using repellents according to their Doctor’s recommendations.
What should a project worker do who suspects he or she
has been infected with WNV?
Any worker who has health
concerns should notify his or her supervisor.
Unpaid project workers (non-employees) should contact the
Guidelines for Protecting Workers
from
Recommendations for Field (Outdoor) Workers
The most likely way persons
become infected with WNV is through the bite of an infected mosquito.
Outdoor workers can decrease
their risk of WNV infection by reducing their contact with mosquitoes through
the use of the personal protective measures listed below. Information about
exposure to insecticides can be found at http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm.
Workers should take the
following steps when working at sites where mosquitoes may be actively biting:
·
Wear
long-sleeved shirts, long pants, and socks when possible.
·
Consider
applying insect repellent to exposed skin, as appropriate and according to
label directions.
·
Do
not apply pump or aerosol products directly to the face; protect eyes at all
times. These products should be sprayed onto the hands and then carefully
patted onto the face, avoiding the eyes and mouth.
·
DEET
(N,N-diethyl-m-toluamide or
N,N-diethyl-3-methylbenzamide) is the most effective insect repellent
available. The more DEET a repellent contains the longer time it will be effective. DEET concentrations higher than 50% do not
increase the length of protection.
·
For
details regarding the safety of DEET, see http://www.nmnh.si.edu/BIRDNET/WNV.html#append
·
If you
use repellents, apply at the lowest effective concentration.
·
Do
not apply repellents to cuts, wounds, or irritated skin.
·
·
Clothing
can be treated with products containing DEET or permethrin,
as mosquitoes may bite through thin clothing, although it may ruin some
fabrics.
·
Permethrin
should only be used on clothing; do not apply it directly to skin.
·
·
Do
not apply repellent to skin that is under clothing.
·
Report in a timely manner all injuries and illnesses of
suspected WNV origin.
Requirements for Workers Handling Dead or Live Birds
·
Use
personal protective equipment that provides barrier protection as appropriate
including gloves, labcoats, chemical
splash goggles if potentially contaminated fluids are present etc. Appropriate
gloves provide a protective barrier that prevents blood and other body fluids
from passing through them.
·
Wash
hands and other appropriate skin surfaces with soap and water after handling
birds and immediately after contact with blood, feces etc., and after removing
gloves and before leaving the workplace.
Workers are at risk of WNV
infection if their skin is penetrated or cut while performing necropsies or
handling WNV-infected tissues or fluids [CDC 2002c].
·
Minimize
the generation of aerosols. If aerosols
may be created, use of a Biological Cabinet (Biohood)
is recommended.
·
Handle
sharp instruments carefully during use.
·
Use
medical devices with safety features when available to avoid sharps-related
injuries.
·
Never
bend, break or recap needles.
·
Dispose
of sharp instruments carefully after use in the appropriate rigid sharps
container; obtain these free containers from CNSM Safety.
·
Report
to the supervisor all needlestick and other
sharps-related injuries.
·
Report
to the supervisor any laboratory incidents or accidents involving possible WNV
exposure.
·
Report
to the supervisor any symptoms consistent with WNV infection.
Additional Requirements for Workers in the
CSULB Animal Care Facility
·
Use a labcoat
provided by the Animal Care Facility while working with the birds. Remove this labcoat
and return it to the storage location before exiting the Facility.
·
Do not wear your
own labcoat into the facility as this may bring
unwanted contaminants into the animal care area.
The
above are basic recommendations to reduce exposure to blood and other tissues
from WNV-infected animals or persons.
More stringent protective equipment and work practices should be used
when warranted; consult CNSM Safety for details. Biosafety
guidelines are available for working with WNV and other microbiological agents
in the laboratory; see CDC/NIH Guidelines for “Biosafety
in Microbiological and Biomedical Laboratories” (http://www.cdc.gov/od/ohs/biosfty/bmbl4/bmbl4toc.htm).
Links to
other Sites with WNV Information
CDC West Nile Virus Home Page
http://www.cdc.gov/ncidod/dvbid/westnile
U.S. Department of
Agriculture Animal and Plant Health Inspection Service, West Nile Virus Site
http://www.aphis.usda.gov/lpa/issues/wnv/wnv.html
CDC/NIH Guidelines; “Biosafety in Microbiological and Biomedical Laboratories (BMBL) 4th Edition”
http://www.cdc.gov/od/ohs/biosfty/bmbl4/bmbl4toc.htm
U.S. Geological Survey
National Wildlife Health Center, West Nile Virus Site
http://www.nwhc.usgs.gov/research/west_nile/west_nile.html
National Institutes of
Health, National Institute of Allergy and Infectious Diseases, West Nile Virus Site
http://www.niaid.nih.gov/publications/wnile/
Food and Drug Administration,
West Nile Virus Site
http://www.fda.gov/oc/opacom/hottopics/westnile.html
State and Local Government Web sites
City of
http://www.ci.long-beach.ca.us/health/organization/eh/vector/default.asp
State and Local Government
Web site links on the CDC West Nile Virus Home Page
http://www.cdc.gov/ncidod/dvbid/westnile
Other Web sites
Cornell University Environmental
Risk Analysis Program, WNV Section
http://www.cfe.cornell.edu/erap/wnv
National Library of Medicine,
Medlineplus West Nile Virus Site
http://www.nlm.nih.gov/medlineplus/westnilevirus.html
National Pesticide
Information Center Web Site, West Nile Virus Resource Guide
http://npic.orst.edu/wnv
CNSM Safety
Website, http://www.cnsm.csulb.edu/services/safety/index.htm
WestNileVirus.SftyTrng.9.04