West Nile virus is an “arbovirus (arthropodborne virus)”
transmitted back and forth between mosquitoes and birds. Humans get infected
when a mosquito decides to have a snack after previously picking up the virus.
The culex mosquito is the most common
culprit to infect humans.
Approximately, 80% of human West Nile infections are
asymptomatic (never know that you are infected). Of those who do develop symptoms the majority
consist of abrupt onset of fever, headache, muscle aches, nausea, vomiting, diarrhea
and a transient rash. So in summary, West Nile virus for the most part looks like
every other viral infection out there. Symptoms usually begin 2-6 days after
being bitten by an infected mosquito. Less than 1% of people infected with West
Nile develop neurologic involvement (meningitis, encephalitis, flaccid
paralysis).
Symptoms involving the brain include high fever,
stiff neck, severe headaches, muscle weakness, mental confusion, tremors,
vision problems, convulsions, paralysis, and loss of consciousness.
These rare manifestations can be dangerous and it is likely these few
cases are where the excitement in the media and parental concern comes from. Neurologic
disease is more common in those over the age of 50. The majority of those who
get neuroinvasive disease will recover.
West Nile first appeared in the United States in New York in
1999 and has subsequently spread across North America. The only place in the
world that has not had a reported case of West Nile is Antarctica (so I guess
moving there is always an option, however, you would likely miss your
pediatricians very much). As of October 16th 2012 there have
been 41 cases of West Nile in the state of Maryland this year, 6 of which have
been in Anne Arundel County (data from CDC website http://www.cdc.gov/ncidod/dvbid/westnile/USGS_frame.html)
Diagnosis of West Nile virus can be confirmed with blood or
cerebral spinal fluid (spinal tap/lumbar puncture) usually having to wait at
least 10 days post-infection to get an accurate result. Because the majority of
patients are asymptomatic and have vague viral symptoms it is not currently
recommended to test for West Nile unless neurologic symptoms are present.
There is currently no direct treatment for West Nile virus.
Fortunately, mild cases of West Nile do not require treatment. However,
children who become severely ill may require hospitalization and supportive
care.
The key to West Nile
virus is prevention.
1.
Eliminate
mosquito breeding sites – Mosquitoes like standing water. Measures to limit
breeding sites include draining or removing receptacles of standing water (old
tires, toys, flower pots, buckets and barrels, pretty much anything that can
collect rain water). Keeping pools and
bird baths clean. Cleaning clogged rain gutters may also help.
2.
Reduce
exposure to mosquitoes – Limit outdoor activity at the height of mosquito
activity, dusk and dawn. Repair or place
screens on all windows and doors to prevent mosquito access to your home. Of note, mosquito traps, bug zappers, and
others marketed to prevent mosquitoes from biting people have not been shown to
be effective and should not be relied upon as the only source of protection.
3.
Use
barriers to protect your skin – Use clothing to protect your skin (ie, long
sleeve shirts, pants, hats). Also available are mosquito nets for strollers and
nets for other areas where children are likely to play outside.
4.
Discourage
the mosquito – Mosquito repellents should be used when outside. There are
many different repellents to chose from containing a variety of compounds (diethyltoluamide (DEET), picaridin,
3-[N-Butyl-N-acetyl]-aminopropionic acid, ethyl ester, or the plant-based oil
of lemon eucalyptus and its synthetic
equivalent p-menthane-3,8-diol). DEET containing products have been used
worldwide since 1957 and has a good safety profile and the concerns of toxicity
in children were unfounded. Adverse
effects appear to be related to ingestion, chronic or excessive use not the concentration
of DEET. Per the EPA and AAP, concentrations up to 30% may be used in children.
Products containing DEET can be used in pregnancy without adverse effects. Children under the age of 2 months should
not use insect repellents secondary to the increased permeability of their skin
and potential for absorption. The higher the percentage of DEET the longer
the protection time provided, however, frequent reapplication is recommended. The EPA does make certain recommendations on
proper application of insect repellents:
a.
Do not apply over cuts, wounds or around the
eyes or mouth (do not spray the face apply to the face with your hands)
b.
Do not spray on a child’s hand as they may then
inadvertently put their hands into their mouth or eyes
c.
Apply just enough to cover exposed skin (do
not apply under clothing)
d.
Wash or bathe after coming inside from using
repellents and wash clothes again before wearing again
5.
If you find a dead
bird: Don't handle the body with your bare hands. Contact your
local health department for instructions on reporting and disposing of the
body. They may tell you to dispose of the bird after they log your report.
References
American
Academy of Pediatrics. Red
Book: 2012 Report of the Committee on Infectious Diseases.Pickering LK, ed.
29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012
American Academy of Pediatrics, Committee on Environmental
Health.Pesticides. In: Etzel RA, Balk SJ, eds. Pediatric Environmental Health. 3rd ed.Elk Grove Village, IL: American Academy of Pediatrics; 2012:515–548
