Slumbering Virus to Awaken Again, Experts Say
April 25, 2000 (Washington) -- Infections by the West Nile virus are likely
to occur again this summer in New York and possibly 17 other states, where the
virus may have spread by migrating birds and mosquitoes, federal officials
confirmed Tuesday. But the majority of these cases are unlikely to result in
severe complications, they added, noting that the greatest danger basically is
limited to high-risk populations such as older Americans.
First reported last summer in New York City, the West Nile virus is commonly
found in Africa, West Asia, and the Middle East and causes encephalitis, or
inflammation of the brain. Spread by mosquitoes that became infected after
feeding on infected birds, it is closely related to the St. Louis encephalitis
virus found in the U.S., common symptoms of which include fever, headaches, and
But unlike the St. Louis version, the effects of the West Nile virus can be
far more severe, resulting in neck stiffness, disorientation, coma, tremors,
convulsions, muscle weakness, paralysis, and even death. During the outbreak in
New York last summer, West Nile virus caused seven deaths and 62 cases of
While initially hoping that this more severe version would not survive the
winter months in America, the CDC last month detected live West Nile virus in
hibernating adult mosquitoes, increasing fears of a possible second outbreak.
Now, federal officials also say that it might have found a new home in America
despite efforts taken last summer in New York and neighboring states to
eradicating the virus altogether.
"We may see some cases here and there over the years," said Stephen
Ostroff, MD, associate director for epidemiologic sciences at the CDC. Putting
it in context, the West Nile virus is an example of the emerging infectious
disease threat facing the U.S. in the age of international travel, he said.
How the West Nile virus made its way to the U.S. remains a mystery. But
federal officials suspect that it may have traveled to New York from Israel
(where a similar outbreak occurred in 1998) through either an infected bird,
mosquito, or human. There are also anecdotal reports of similar cases reported
during a 1996 Romanian epidemic.
The good news is that the West Nile virus might not represent that
significant of a threat to healthy Americans. In a survey conducted in New York
City following last summer's outbreak, the CDC found that only about 2.5% of
the entire population in the highest-risk area actually were infected, with the
majority experiencing mild to moderate symptoms, Ostroff said.
Fearing a second outbreak, health authorities in New York, New Jersey,
Connecticut, and Pennsylvania have also already launched an aggressive campaign
to attack contaminated mosquitoes before they mature into adults. The plan
includes a public education campaign aimed at eliminating areas of standing
water, where mosquitoes breed.