West Nile virus took a summer vacation, cases drop to record lows
BY BLYTHE BERNHARD
POST-DISPATCH
10/03/2009

One unlucky 50-year-old woman from Chariton County caught the only reported case of West Nile virus in Missouri this year. The story is similar in Illinois — four cases in the whole state — and nationwide.

Just a couple of summers ago, the West Nile virus infected thousands, killed hundreds and kept people inside to avoid lurking mosquitoes and dead birds that can carry the disease.

Now, the virus seems to have gone into hiding.

"It's just astounding to us how the activity has dropped off," said Karen Yates, vector-borne disease coordinator for the Missouri Department of Health and Senior Services.

So what's happening?

There are several theories about the absence of West Nile. Yates points to cooler than average summer weather and regular rains that have kept mosquito activity down. An expert at the Centers for Disease Control and Prevention hopes that people have gotten the message about insect repellent: "If you stop a mosquito bite, you're going to stop infection," said Emily Zielinski-Gutierrez of the CDC.

And then there's the H1N1 virus (swine flu) effect. The two viruses share some symptoms — fever, body aches. Some epidemiologists think that doctors might be watching for swine flu when a patient complains of those symptoms.

Doctors have long been trained to look for West Nile when a patient has a fever in the summer because flu doesn't usually circulate in the season. But H1N1 changed that by staying active throughout the hotter months and gaining lots of attention.

One local clinician said he doesn't think doctors are confusing the viruses. For one thing, the viruses tend to strike different groups of people. Older folks are more vulnerable to West Nile, and younger people have higher rates of contracting swine flu.

Plus, the H1N1 virus causes respiratory symptoms of cough and sore throat that aren't typical in West Nile infections. And West Nile cases started dropping off even before H1N1 showed up.

"It seems to me there is more to it," said Dr. Farrin Manian, chief of infectious diseases at St. John's Mercy Medical Center. "I don't really see clinicians missing a lot of West Nile virus."

Manian suspects that the decrease in West Nile is legitimate, and not the result of less testing or reporting. He wonders whether after 10 years of exposure to West Nile, people have developed greater immunity to it. Already, it's thought that 80 percent of people who get infected never develop any symptoms.

The most serious West Nile cases, affecting less than 1 percent of people who catch it, can cause meningitis or encephalitis (inflammation in the brain or spinal cord). Those patients are typically hospitalized and given a battery of tests, which would always include West Nile.

Last year, almost 700 people nationally had West Nile meningitis or encephalitis, and this year the diagnoses dropped to fewer than 200. Twelve people have died from the virus in the U.S. this year, down from a high of 284 in 2002.

There could still be a wave of West Nile into October, particularly if temperatures stay high. The latest cases have shown up in Missouri in late October, and testing shows there are still mosquitoes flying around with the disease here.

The woman from Chariton County recovered from West Nile virus.

The problem with understanding viruses is their unpredictability. And 10 years of surveillance of the West Nile virus is not enough to determine true trends, said Zielinski-Gutierrez, who isn't making any predictions for next year.

She said, "While we're glad that this year was quiet ..."there's never going to be a time where we can tell people, 'Don't worry about it, put the repellent away."

http://www.stltoday.com/stltoday/news/stories.nsf/sciencemedicine/story/BACFC5CABA44826286257643007C8F9B?OpenDocument

Only one case in Missouri and four in Illinois this year.

St. Louis had people die from it last year.

I was reading that about the West Nile pattern a couple years ago. It spread across the country east to west like a wave. and behind each wave resistances were up and few people were catching it

when it hit the west coast it stopped and now its slowely dying out

I didn't know that. I'm glad that it's dying out though.

"Last year, almost 700 people nationally had West Nile meningitis or encephalitis, and this year the diagnoses dropped to fewer than 200. Twelve people have died from the virus in the U.S. this year, down from a high of 284 in 2002."

It certainly is very good news. Now if only the same fate would befall the H1N1....That would be lovely.

I worked with our local Insect and Vector control office to put on a series of presentations this summer for our city on preventing WNV. The Antelope Valley, where I live, had a bit of a spike this year and we saw 9 cases. The DEET Education program also helped out by donating over $1000 in insect repellent. I do a lot of outdoor evening (dusk) meetings in the summer and you can bet I was wearing my insect repellent and brough enough for everyone at the meeting. It's not something I'd want to risk getting. I'm glad to hear the numbers are dropping.

A "mild" case can you out of commission for up to 60 days. Of course, that's better than the severe cases. And, of course, very few people get sick from it at all. But, I know I can't afford to be sick for even a week, let alone up to 60 days.

Wow, you did all of that Ruth. That's really neat.

St. Louis had an aggressive approach to the West Nile. We were having people die from it.

We had one person die from Swine Flu last week.