Doctor says mosquitoes still biggest health threat

2/28/2006

DETROIT - Take it from "West Nile Lyle": You may have heard a lot about bird flu, but this coming summer, we've got more to worry about from mosquitoes than birds.

True, it's not exactly mosquito weather outside. But Dr. Lyle Peterson, the federal government's top West Nile virus expert, warns that despite a lull in virus activity nationwide, the mosquito-borne disease is still out there.

"I guarantee the average person around here has more to worry about from West Nile virus than bird flu," said Dr. Peterson, whose neighbors tease him about his specialty by calling him West Nile Lyle.

He spoke yesterday in Detroit to mosquito control experts from around the country who were attending the annual meeting of the American Mosquito Control Association.

Dr. Peterson, who is the director of vector-borne infectious diseases at the federal Centers for Disease Control and Prevention, knows his warnings are a tough sell.

West Nile virus was in the headlines all summer long in 2002. That year, Ohio and Michigan respectively had the second and third-highest number of West Nile virus cases in the country. The virus infected 441 Ohioans, killing 31. In Michigan, there were 614 cases and 51 deaths.

But West Nile virus practically disappeared from the headlines after cases began plummeting. In 2005, there were 58 cases of West Nile virus in Ohio but no fatalities. Lucas County had four cases. Michigan had 62 cases and four deaths.

What low numbers like this don't show, however, are how many people have been infected by the virus but no one found out. Dr. Peterson said most people who are infected never get sick, but about 20 percent develop symptoms ranging from fever to brain swelling. The case numbers tracked by the CDC and state health departments overlook all the cases of people who develop a mild case of West Nile and just call in sick and stay home to recover.

Well, to say "mild" may not be the most apt description. Dr. Peterson became ill from the virus himself and said "I was flat on my back for a week."

Recent estimates by the CDC peg the actual number of people infected with West Nile virus since 1999 at 1.3 million, with about 315,000 of those people developing milder cases of the disease. That's far higher than the nearly 20,000 cases nationwide reported since 1999. But again, that number is likely only from those sick enough to go to the hospital or doctor.

"The public health impact of West Nile virus has been grossly underestimated," he said. "There's been an irrational hope that West Nile virus is going away, but it's certainly not going to."

The difficulty is experts can't predict when the virus might flare up again. It seems to do best during hot, dry summers, but it's hard to know for sure.

Once infected with the virus, you won't catch it again. And at some point, most eventually will build up resistance to it. But that could take many generations, Dr. Peterson said.

Given that the U.S. population is about 300 million, the estimate of 1.3 million people infected so far means most people have not yet been exposed.

Dr. Peterson worries that the general public as well as local and state officials may begin to ignore the threat of West Nile virus and let their guard down. As it is, despite the emergence of the virus in 1999, few counties and cities have active mosquito control programs.

In Ohio, Lucas County has the most active mosquito-control effort in the state, according to Joe Lynch, president of the Ohio Mosquito Control Association. Most counties or cities have either no program at all or a limited effort that includes only partial control efforts, he said.

In Michigan, only four counties have comprehensive mosquito-control programs.

Randy Knepper, president of the Michigan Mosquito Control Association, doesn't expect things to improve.

"Michigan had 51 people die in 2002 and nothing was done. There was no funding," he said.

But back to bird flu.

One reason that disease has been in the news so much is it's the latest example of how quickly a disease can spread in the modern world. But the same is true for mosquito-borne diseases. Already, mosquito-borne diseases are popping up in parts of the world where they've never been before, Dr. Peterson said.

So heed the words of West Nile Lyle when he says the emergence of another mosquito-borne disease like West Nile virus is "inevitable. Who knows what the next thing is?"

Contact Luke Shockman at:

lshockman@theblade.com

or 419-724-6084.