>Kriss Costa


>West Nile Virus



>When West Nile virus (WNV) first appeared in the US in New York in 1999,

>little was known about this killer disease, except that it was transmitted

>by mosquitoes. As WNV spread across the US, it became the fastest moving

>vector-borne disease the country had ever seen, going from coast to coast

>in less than 4 years, when it entered California in 2003.



>Kriss Costa, of the Santa Clara County Vector Control District, will talk

>about the background of WNV and the reasons believed why it was able to

>spread so quickly through the US, as well as the methods of transmission

>and its symptoms. Kriss will bring you up to date as to what WNV is doing

>in 2004 and what California, including Santa Clara County and the Bay

>area, is doing to prepare for the coming of WNV.


Kriss began her talk by explaining that WNV is primarily a bird infection. The majority of birds contract WNV through the bite of an infected mosquito, but it has been discovered that birds may pick up the virus when they browse through the feces of infected birds. It has spread rapidly across the USA because during the winter migratory birds from different flyways mingle in Central and South America. Then once the birds bring it into an area, the disease establishes itself there and becomes a fact of life. It has now been found in a number of species, not just birds, and we need to be prepared for more unwanted surprises.

Four-fifths of the people exposed to WNV, almost always from mosquito bites, never develop any symptoms. For most of the rest it amounts to a mild flu-like condition lasting one to several weeks. (If you are sick for more than six days, you should see your doctor immediately.) However, there have been some very serious cases: encephalitis, meningitis, or even polio-like paralysis lasting for some time. There have also been several fatalities each year.

The most serious effects are felt the second year the disease is around, because that is when the largest percentage of the vulnerable population is hit. After that most people have been exposed to the disease, so normal healthy immune system responses keep the threat down. (Children and older people are more vulnerable, and the virus can be transferred in utero.)

The best way to prevent WNV is to keep mosquitoes from breeding in your world. To do this, make sure there is no standing water in your yard. Important places to look are rain gutters, old tires, and ornamental fountains with standing water in them. To prevent mosquitoes from breeding in bird baths and other small ponds, change the water completely at least once a week. For larger water bodies, seeding them with mosquito fish (so named because they eat mosquito larvae) is a good step. Puddles caused by leaky faucets can be prevented by fixing the leaks. There are also mosquito-specific chemicals you can use that make a big difference. Hardware stores sell them in donut, pellet, and spray form.

During Q&A a number of interesting points came up:

The Santa Clara County Vector Control District (SCCVCD) will be glad to stock your pond with mosquito fish. Contact them at 408-792-5010 for more information.

When WNV first hits a bird population, we find out about it because the birds start literally falling out of the sky. The Santa Clara County Vector Control District is currently testing dead birds to see if they have WNV. If you see a "healthy dead bird", meaning one that hasn't decomposed yet, please let SCCVCD know about it. If it tests positive for WNV, they will forward it to the State Authorities.

Tian Harter

Click here to visit the CDC has a great WNV page.