This summer, children who are immunocompromised because of cancer or organ transplant should always apply mosquito repellant before playing in outdoor areas where mosquitoes
are plentiful. For practical reasons, it is advisable for high-risk
children to avoid these areas altogether in early evening, when mosquitoes
are especially active.
The signs of West Nile virus (WNV) are similar to enteroviral
meningoencephalitis. Diagnosis can be made retrospectively by sending a
serum sample to the State Hygienic Laboratory. There is no specific
antiviral therapy at this time, and there is no WNV vaccine for humans. (There is a WNV vaccine to protect horses.)
For healthy children, adolescents and younger adults, there
appears to be little or no risk from WNV infection. As with other viruses a
natural infection early in life will protect the person from a life-threatening infection in late adulthood.
At least one case of congenital WNV infection has
been detected in a newborn, whose mother was infected during pregnancy. The
mother was never seriously ill.
Some background on West Nile virus
The West Nile virus is in the family of Flaviviruses. Famous members of
this family cause dengue fever, yellow fever and Japanese encephalitis.
Many of these viruses are carried by mosquitoes. Yellow fever is renowned
because it was one of the reasons the Panama Canal project was such a
difficult task. Japanese encephalitis virus continues to be a feared virus
in many countries in Asia. There are now vaccines that will protect humans
from disease following infection with either of the last two viruses.
WNV first was detected in the United States in 1999. WNV was
discovered after several elderly people died from meningo-encephalitis. The
people lived in and around New York City. The geographic source of this
virus has not been determined. Since WNV originates from Africa, one
reasonable possibility is that the virus was imported into the United States within
exotic birds, such as parrots, imported from Africa for pet shops in New
York. The infected exotic birds would transmit the disease after being
bitten by mosquitoes. In turn, the mosquitoes would transmit the virus to
birds native to North America. Crows appear to be particularly susceptible
and may die from WNV infections. When infected crows are bitten by
mosquitoes, in turn, the mosquitoes can transmit the disease to humans.
The WNV has now spread along the East Coast and also westward to Illinois
and Iowa. There were about 4,000 human cases of WNV disease in the United States in
2002. Chicago was especially affected. In all likelihood, the number of
cases in Iowa and Illinois will increase this summer.
The elderly are
especially prone to develop severe disease. Because WNV poses a serious health risk to the elderly, they, too, should follow the precautions noted above:
- Always apply mosquito repellant before spending time in outdoor areas where mosquitoes
are plentiful.
- Avoid mosquito-infested areas altogether in early evening, when mosquitoes
are especially active.
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