Fall–Winter 2003
(Note: The next WNV update will appear in January 2003)
Fifteen human cases of West Nile virus infection have been reported in Massachusetts, as of Nov. 6, 2003. The infected individuals reside in Medford, Watertown, Woburn, Newton, Swansea, Westborough, Arlington, Fitchburg, Chicopee, Somerset, Weymouth, Worcester (two cases), Uxbridge, and Boston. The case from Swansea was the first West Nile virus infection in Massachusetts identified through the national blood donor screening program.
Because West Nile virus activity was documented in more than 150 Massachusetts towns, and WNV-positive birds were found in every county in the Commonwealth, the State Laboratory is no longer routinely recording reports of dead birds or testing dead birds for WNV this year. The State Laboratory will continue to test suspect human and horse cases for the virus.
How Do People Get Infected with WNV?
West Nile virus is a parasite that lives in the blood of mosquitoes, animals, and humans. When viral levels reach a high enough concentration in a host's blood, feeding mosquitoes become infected and can transmit the virus back to animals and humans. While West Nile virus has many hosts, scientists consider the bird to be its principal reservoir.
In a very small number of cases, West Nile virus also has spread through blood transfusions, organ transplants, breastfeeding, and during pregnancy from mother to baby.
What are symptoms of WNV?
Most West Nile infections are so mild that the vast majority of victims have no symptoms at all. Another 20% of people who become infected will display mild symptoms that include fever, headache, body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash.
Only 1% of the people bitten by a West Nile-infected mosquito will develop a life-threatening neurological illness. In these rare instances, the virus can wreak havoc on the brain, causing cerebral swelling (encephalitis) or inflammation of the membranes enveloping the brain and spinal cord (meningitis).
Severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.
If you think you have symptoms of West Nile virus, contact your health care provider.
People over the age of 50 who get infected with West Nile virus are more likely to develop serious symptoms, and should take special care to avoid mosquito bites.
Preventing West Nile Virus
The threat of West Nile virus exists whenever mosquitoes are active, typically at dawn and dusk. Marlborough residents can protect themselves from mosquito bites by taking some simple precautions:
w People who spend time outdoors, especially in places attractive to mosquitoes, should wear loose, long-sleeve shirts and loose pants.
w When outdoors, residents should also apply insect repellant that contains DEET to exposed skin. Adults should use repellant with less than 30% DEET, while children should wear repellant that contains no more than 10% DEET. Repellent containing DEET is not recommended for infants younger than 2 months of age.
w Residents should make sure their windows and door screens are in good repair.
w Marlborough residents, landlords, employees and business owners should eliminate standing water in their neighborhoods. Water that remains stagnant for seven days or longer can serve as a mosquito-breeding habitat.
w Standing water frequently collects in old tires, trash barrels, clogged gutters, wheelbarrows, fishponds, birdbaths, pots, small pools, and discarded containers.
w Families should keep children's wading pools empty and on their sides when they aren't being used.
w Residents should replace water in bird baths weekly.
Please remember that water in streets is not likely to harbor mosquito larvae unless it remains undisturbed for a week or so (cars driving through puddles make it very difficult for larvae to progress to adulthood).
West Nile Virus Activity in 2003
From spring to late fall, public health officials monitor West Nile virus activity in vulnerable mosquito and animal species. Because mosquitoes, birds, and horses, in particular, often contract the virus well before a human case is identified, the presence of WNV in these populations helps health officials predict and prevent human infections.
Birds that test positive for the West Nile virus are often the first indication that the disease is present in a community. Horses are another sentinel for WNV because their high exposure to mosquitoes makes them more likely to be infected than people.
Once the virus has been detected in a community, health officials in many states (including Massachusetts) shift their attention to mosquitoes. Unlike monitoring birds or horses, mosquito-based surveillance provides quantifiable information on the potential risk of WNV infection to humans and domestic animals.
Whom should I call to report standing water or a dead bird?
Birds found on private property should be disposed of by the owner or management.
| 
