The Encephalitis Outbreak In New York In 1999

In the late summer of 1999, there was an epidemic of encephalitis and meningitis in New York. Initially, all the victims came from an eight square kilometer region centered on Queens and the Bronx.

Later, it spread further, although there were merely 59 cases and seven deaths – all in older people. 677 individuals were tested in the original survey, 19 of which tested positive for meningoencephalitis.

Going by the size of the population of New York, it was estimated that between 3,500 and 13,000 individuals (average: 8,200) had contracted West Nile virus. There were almost certainly much more than that, but serious symptoms usually only show in the young and the old.

Those in the in-between age group almost certainly thought that they had a bad cold, which means that fewer than one percent of victims displayed severe neurological symptoms.

At first, it was wondered whether this outbreak could be the result of an act of terrorism, but others suspected mosquitoes. Investigation concentrated on St. Louis encephalitis. However, when it was thought to check for West Nile virus, the number of cases increased.

The cause of the epidemic was soon confirmed to be a West Nile-like virus based on the identification of viral infection in human, avian, and mosquito samples.

This had not been expected because the New York outbreak was the first time that West Nile virus had been seen in the Developed world.

Then recent bird deaths were remembered. Large numbers of wild birds, especially crows, had died recently in the region and there were deaths at the Bronx Zoo of exotic birds as well.

Examination of the corpses of these birds showed traces of encephalitis which resembled West Nile virus (WNV). When doctors knew what to look for, they discovered comparable traits in the brains of the dead humans

The authorities immediately initiated extensive measures to reduce the numbers of Culex pipiens, the mosquito in the area that specializes in biting birds. The public was informed and helplines were established – by the end of September over 150,000 calls had been made.

The local authorities continued to spray and handed out 300,000 aerosols of DEET and 750,000 public health leaflets, which recommended tidying up the garden, not going out at dusk or dawn and covering up bare skin.

WNV is an arbovirus (arthropod-borne virus), which means that it is transmitted to humans by arthropods (insects), normally the tick or the mosquito. Previously, WNV had only been seen in Uganda, where it was first discovered and in isolated cases in Europe and South Africa.

A report concluded that it was “unclear whether the virus that caused this outbreak is a previously identified strain of WNV or a new variant”, however now recent evidence seems to suggest that a new mosquito – a hybrid of C. pipiens – living in the New York metro was to blame.

This is still not definite, but if it is true, then the whole world ought to take care, because the New York ‘hybrid’ is related to the London Underground mosquito which inhabits nearly every underground railway system on the planet.

Owen Jones, the writer of this piece writes on several topics, but is currently involved with finding a home remededy for mosquito bites. If you would like to know more, please go to our web site at Getting Rid of Mosquito Bites.

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