Wednesday, August 29, 2012

Don't Let West Nile Keep You Indoors

A few Mid-Michigan residents have complained to me that they don’t know what to make of the reports in the news about West Nile Virus.  They tell me they are hearing that it is the worst West Nile year ever, yet they don’t think they have ever met anyone who has had the disease.  People say they don’t know whether they ought to be worried, or just ignore it. Let me tell you what I feel:  I feel deeply appreciative of the US Center for Disease Control’s (CDC) amazing ability to track rare and novel diseases, knowing that someday, when a truly deadly new disease appears, we will be warned and ready.  Meanwhile, I’m going to enjoy Michigan’s outdoors without undue fear.

West Nile Virus first appeared in the US in 1999 and is now widespread. It is transmitted by the Culex mosquito and makes a variety of mammals and birds ill.  Most years there are a few dozen human deaths from the disease in the US.  It also kills horses and birds.  There is no vaccine for the disease for humans, but horse owners should get their animals vaccinated.  Most people who get bitten by the Culex mosquito never have any symptoms and may become immune to the disease. A few people who get bitten become sick and go to the doctor and on rare occasions may die. When you hear about the number of “cases” of West Nile Virus, it is these people who have become very ill and have been tested who you are hearing about. Not included in the number of cases are the thousands who actually had the disease but had no symptoms.

This year the number of cases and deaths will likely be double what we usually see.  No one is sure of the reason--maybe the mosquitos are doing better in the warmer weather.  There have been about 100 cases in Michigan so far, and 4 deaths.  Remember that about 1,000 people are killed in car crashes in Michigan every year, and nearly 30,000 die from heart disease.  Comparing the numbers you can see that even with the increase, West Nile is not a big a threat at this time.

People ask if we should spray for mosquitos or put chemicals in ponds to kill larvae.  Some municipalities in Texas have started doing that. In general, this is likely to do more harm than good.  Effective mosquito control programs are carefully managed, and have good historical data to guide local governments on what works, what is harmful to the environment, and what is just a waste of money.  It is almost always the case that rushed anti-mosquito programs don’t kill enough mosquitos to make a difference.  If West Nile deaths continue to climb, mosquito control could be part of a prudent response.  But it would have to be done wisely to have any real benefit, and to avoid harm to the environment.  

There are some people who should not get bitten by mosquitos, because West Nile Virus could harm them.  The very old, infants, and people with illnesses like diabetes, a heart condition or an immune disorder should take precautions including wearing long sleeves, using repellant, and staying indoors at dawn and dusk.  Everyone else should remember that healthy outdoor exercise will prolong their lives and head out the door confidently.  Don’t let the headlines scare you into staying inside.

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