Sunday, August 12, 2007

West Nile Threatens Connecticut

Once Bitten...
Due to recent weather patterns, the state's mosquito population is exploding. Is Connecticut set for a West Nile virus outbreak?
By Adam Bulger
Hartford Advocate, July 5, 2007

With a recent spike in Connecticut's mosquito population, some state health officials are cautioning that mosquito-borne illnesses, including the West Nile virus, may increase this year.

The University of Connecticut's Agricultural Experiment Station, which traps and monitors hundreds of mosquitoes at 91 locations throughout the state, has noticed unusual growth in the state's insect population. Over the past 10 years, the traps have yielded an average of 225 mosquitoes per trap. In the second to last week of June they collected mosquitoes 350 per trap, and the chief medical entomologist for the CAES, Theodore Andreadis, predicted the weekly average would rise as the summer progresses.

More mosquitoes doesn't just mean ruined picnics.

"We have conditions right now that are quite suitable for rapid amplification for the West Nile virus," Andreadis said."Why I'm saying that is because if you have a very wet spring with a lot of flooding that produces a lot of mosquitoes, if that's followed by very hot weather, like we have right now, that seems to accelerate the whole transmission cycle."

The CAES has monitored mosquitoes as part of the state's mosquito management program, a coordinated effort between the state's Department of Health Services, the state's Department of Environmental Protection and the CAES, since 1997.

Andreadis and his team sort through the mosquitoes to determine what kind of mosquitoes they are — Connecticut hosts about 50 different species of mosquitoes. Determining the species is critical for determining whether they are nuisances or health risks. Different types of mosquitoes can carry different kinds of diseases.

West Nile is carried by the Culex mosquitoes, which are found typically in urban and suburban areas, and Eastern Equine Encephalitis, a disease whose symptoms range from mild flu-like coma and death according to the Center for Disease Control, is spread by Culiseta mosquitoes, which are found in rural places with fresh water marshes. In Connecticut, Hartford and Fairfield counties have historically had the most cases of West Nile, while the southeast region of the state is hit hardest by Eastern Equine Encephalitis.
The main infection time for West Nile is August and September.

"You'll see people start getting sick in the last two weeks of August. The peak of people getting sick and coming down with clinical signs, is in early September," said Randall Nelson, a veterinarian for the DHS.

While cases have already been reported in other parts of the country, it hasn't yet reared its head in Connecticut.

The first outbreak of West Nile was in Connecticut's southern neighbor, New York, in 1999. Despite its proximity to the disease's presumed source, Connecticut residents have so far mostly avoided the disease.

"We've been very lucky. Why that is, we're not 100 percent sure. But while some people were seriously ill, and we have had several deaths, in the big picture, if you put it in perspective, we have been quite lucky," Nelson said.

According to the state health department, only 57 Connecticut residents have contracted West Nile (five of those contracted the disease out of state) since the state began monitoring for the disease. In those cases, there have been three fatalities.

I suggested to Nelson that Connecticut is a smaller state, and that the smaller population would account for the lower rate of infection. Nelson disagreed.

"Of course, you need to have a population at risk to get sick," Nelson said. "But beyond that, we do have over three million people living in Connecticut in a variety of residential settings, from rural to urban. So, we certainly have opportunity."

West Nile is a difficult public health risk to assess. Despite years of close study by health officials throughout America, it's impossible to determine how it will spread.

"It has to do with a number of factors, but I don't think we know everything that comes into play," Nelson said, adding that while public health officials have learned a lot about the disease since 1999, there are still many unknowns. "To predict where it's going to crop up, we can't really do that."

Statistically, only one out of 150 people exposed to the virus will show symptoms. And when symptoms are evident, they vary greatly.

"It varies from mild symptoms — some people will just very mild symptoms — a fever, headache, not much more than that," Andreadis said. "But other individuals will develop much more severe complications like nausea or vomiting. The virus can affect brain cells. You can slip into a coma and die."

The best treatment for the virus is avoiding getting bitten by mosquitoes. That doesn't mean we need to stay inside througout August and September. Commercially available insect repellent sprays containing DEET are a reliable method of avoiding mosquito bites. He cautioned people from relying on citronella candles marketed as fighting mosquitoes, as he said the candles are ineffective. Nelson recommended that Connecticut residents outfit their windows with screens to keep mosquitoes out of their homes, and to employ netting for outdoor activities like camping. Because mosquitoes lay eggs in water, emptying out containers that have been filled with water is important.

Andreadis said that Connecticut residents should get used to taking these simple precautions against West Nile, as it has become part of the landscape.

"I don't think, given our ecology, given the species of mosquitoes that carry the virus and our mosquito season, we're probably ever going to experience the volume of cases you see in other parts of the country," Andreadis said. "But you have to understand that this virus has found a permanent home. It's firmly established in North America and Connecticut. It emerges every year."