Connecticut Winning Battle Against Encephalitis

By Jeff White

Dr Theodore Andreadis, chief medical entomologist for the Connecticut Agricultural Experiment Station in New Haven, is out of breath on the phone these days.

The doctor is part of the team of researchers, veterinarians and biologists spanning several governmental and non-governmental agencies that have recently taken up the battle against the West Nile-like encephalitis that has crept over Connecticut’s borders. Since its outbreak in the New York metropolitan area shortly after Labor Day, the virus has been confirmed responsible for six deaths. But Connecticut’s experience with West Nile-like encephalitis has thus far been limited to the world of mosquitoes and birds, state health officials say.

“At this point, we have no human cases in Connecticut,” Dr Andreadis said recently. “We’re continuing to trap mosquitoes throughout lower Fairfield County. To date [October 7] I think we’ve trapped and tested close to 2,500 mosquitoes since this whole thing began after Labor Day.”

These trappings have been successful in isolating two pools of mosquitoes infected with the virus near  a Greenwich golf course on October 4. The isolates, coupled with a score of dead crows found in Westport and Stamford — eight of which have tested positive for the virus — have helped health experts to track exactly how far the New York outbreak has spread into Connecticut.

The virus — which is characterized by extreme headaches, muscle aches, and in its most severe cases, the failure of the central nervous system — is on the decline, health officials say, a conclusion drawn from a variety of environmental and seasonal observations.

But while mosquito and crow analysis continues, experts from Connecticut’s Department of Environmental Protection (DEP) and Department of Public Health (DPH) still urge residents to remain vigilant in protecting themselves from mosquito bites.

The Battle Against An Unwelcome Visitor

The virus has been dubbed West Nile-like because of its striking resemblance to a virus that previously has been found in Africa, Asia and Europe. That virus is called West Nile.  Dr Theodore Andreadis explained that genetic work is not yet complete to definitively conclude that West Nile-like and West Nile are the same virus.

Symptoms of the virus vary from mild illness — such as low-grade fever, a headache and malaise — up to symptoms of encephalitis, which may include high fevers, extreme neck pain, and disorientation.

Most people who are infected do not exhibit any symptoms, or at worst might develop some minor illness before making a full recovery. In some individuals, particularly those with weaker immune systems like infants and the elderly, the West Nile-like virus may cause serious disease that affects the central nervous system. At its most extreme, it may cause permanent, even fatal, neurological damage.

For now, experts believe only mosquitoes spread the virus, explained Dr Randall Nelson, a public health veterinarian in the DPH’s division of infectious disease. “What happens as far as we know is that the virus circulates primarily among birds. Some species of mosquitoes bite birds, and can spread it from bird to bird by their bites.

“What happens from a public health point of view is that over time, if there are enough birds and mosquitoes, and mosquitoes have enough time to bite birds and pass [the virus on], you get the situation of many infected birds and many infected mosquitoes. And then, by chance, people may be bitten by mosquitoes.” 

Symptoms generally occur 5 to 15 days following the bite of an infected mosquito, and range from a slight fever, headache, rash, swollen nodes and conjunctivitis (irritation of the lining of the eye) to the rapid onset of severe headache, high fever, stiff neck, disorientation, muscle weakness, coma, or death. But according to Dr Nelson, “Only 1 in 300 people that are bitten from an infected mosquito will develop any clinical symptoms."

The battle of containing the virus in Connecticut has focused on southern Fairfield County, in the towns of Greenwich, Westport and Stamford, where the largest concentration of dead crows has been found. These crow corpses so far have been the tell-tale sign for the West Nile-like virus, according to Dr Andreadis, because for whatever reasons crows seem the most susceptible to the disease.

For researchers, the crow has been a sentinel for viral activity in broad geographic locations. “We’ve been testing crows that have been found to die potentially from this particular virus to get an idea of the extent of virus activity in [Connecticut],” Dr Randall Nelson said. 

Many of the crows tested for West Nile-like have come back positive for the virus, which came as no surprise to Dr Nelson. “Just because we report an isolation from a crow in a particular town, that doesn’t mean that that is where it acquired it, because they have a 50 mile flight range; so we don’t know where they are picking it up.”

In all, there have been approximately 80 places in the state where trapping has occurred since September. Thirty-seven of these sites are used every year to monitor occurrences of Eastern Equine encephalitis. The remaining test areas were erected in towns bordering Westchester County, New York. 

Until very recently, these border towns have been blanketed by Scourge, a low-level pesticide that kills mosquitoes. However, with the onset of cooler days and cold nights, Scourge is not effective against the insect, and spraying has ceased in southern Fairfield County.

Though thwarting the pesticide offensive, the less temperate weather of autumn and winter might prove to be the best weapon against the West Nile-like virus; health experts are confident of several indications that the encephalitis outbreak poses little danger to local residents.

Little For Residents To Panic About

“The weather is working in our favor,” surmised Dr Theodore Andreadis recently. “ The cool weather we’re having right now will decrease [mosquitoes’] feeding activity. Generally, below 50 degrees, mosquitoes are not active at all, so with the cool nights that we’re having there has been very little activity.”

“The risk of being bitten is quite low,” he added.

The fact that there have not been any other encephalitis isolations in mosquitoes since the October 4 findings in Greenwich is good news for researchers. As Dr Andreadis explained, the more mosquitoes researchers trap and test, the more reliable the data is. With close to 2,500 mosquitoes trapped and tested, the data looks good. “If we were to have multiple isolations of the virus, I’d be much more concerned. But we’re not finding that,” he said.

Statistics gathered by the Connecticut DEP offer more evidence that residents should not panic about West Nile-like encephalitis. The likelihood of being bitten by an infected mosquito is quite rare, according to information supplied by the DEP. Only about 1 in 1,000 mosquitoes are infected, so even if a person living in an area where West Nile-like virus has been reported is bitten, “They are not likely to get sick,” said Michele Sullivan, DEP Communications Director.

“We believe that the virus is on a decline,” said Mrs Sullivan.

And for the most part, experts are not too concerned about the virus being carried south as Connecticut birds migrate for the winter. As Jim Sirch, director of education at the Connecticut Audubon Center in Fairfield, explained, at this point the only species of birds that researchers are concerned about are crows, which do not migrate.

“With the cool temperatures, the mosquitoes are not actively feeding, so even if there are birds carrying the virus, [mosquitoes] are not going to be feeding on these birds, so you’re not getting any additional transmissions,” said Dr Nelson.

Health officials say people still need to take precautions against being bitten from a possibly infected mosquito. Some species of mosquitoes like to breed and live near standing pools of water, so eliminating stagnant water found in gutters and on driveways is highly recommended.

Dr Nelson suggests wearing long sleeve shirts and pants to reduce the number of mosquito bites incurred, along with wearing an insect repellent that contains DEET and utilizing mosquito netting over baby carriages when walking around with small children.

Mosquitoes typically are most active in the hours preceding dawn and dusk.

“We don’t really know whether or not this virus will be able to establish itself on this continent yet,” said Dr Nelson. “That question may not be answered until next year, when further bird testing and mosquito testing will be performed.

“The hope is that [the virus] slows down to a point where the risk to humans is very, very small.”