Nile River Encephalitis
by Dr. Stephen Blythe
http://www.travelhealth.com
The Western Nile River encephalitis virus, fairly common around the world but never before seen in the Western hemisphere, has now been found to be responsible for the latest encephalitis deaths in the New York City area. This points out three main issues: 1)"emerging" infectious diseases are a constant threat to the U.S., 2) there are few places safe from insect-carried disease, and 3) the increase in world travel means diseases will spread farther and faster. It has been speculated that this virus was introduced by someone smuggling a bird from Africa to the U.S.
Western Nile River encephalitis is not much different than St. Louis encephalitis, so in many ways it is not a different threat than previously existed along the east coast, and it is dealt with through mosquito control and monitoring. (Large groups of chickens are exposed to the outdoors and monitored for encephalitis. The percentage of birds getting the virus is an indicator of how prevalent the virus is. One difference in this virus and the St. Louis strain is that it kills birds.) The wet weather may have allowed it to get a grip with associated increases in mosquito populations. Public health officials have two concerns right now. First, will the virus survive the winter season and reemerge in the springtime? Second, since the virus may survive in birds and be picked up by mosquitoes for 20 to 100 days, will the virus now spread southward with migrating flocks of birds? This virus has been shown to migrate into northern Europe with the springtime northward duck migration.
Case fatality rates for this virus average about 10%, with the elderly and very young at greater risk. As with other types of encephalitis, some who survive may be left with neurologic/mental impairment.
Anywhere there is encephalitis of these types, usually spread by evening-feeding culex mosquitoes, good insect prevention techniques should be used by those who will be outdoors in the evening. Here in Florida during encephalitis epidemics, evening school ballgames are frequently rescheduled to weekend afternoons. It becomes a way of life.
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