Two Mosquito Pools Tested Positive For West Nile Virus, Boston, Massachusetts

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Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Public Health
Article Date: 01 Sep 2010 - 9:00 PDT

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The Boston Public Health Commission reported today that two more mosquito pools have confirmed contamination of West Nile Virus (WNV), one pool was detected in North Dorchester and the other one in Hyde Park (first time this season).

Authorities inform that previous infected mosquito pools had been found in North Dorchester and West Roxbury.

Experts say that when more than one mosquito pool tests positive for WNV it is most likely to be present throughout the city. One human case of WNV infection, a 46-year-old Boston female was confirmed last week. Health authorities inform that the patient has since recovered.

The Boston Public Health Commission says larvacide has been placed into city catch basins since June - the aim being to reduce the mosquito population in the city. A larvacide is a substance used to kill harmful larvae. Larva (plural: larvae) is the newly hatched, wingless, often wormlike form of many insects, in this case mosquitoes.

Although spraying has been done to control nuisance mosquito populations in some areas of town, there are no current plans to extend spraying throughout the city.

What is West Nile Virus?

West Nile Virus, also known as WNV, is a virus of the family Flaviviridae which is spread by the bite of infected mosquitoes. The Flaviviridae virus family also includes Japanese encephalitis, yellow fever and dengue fever.

WNV mainly affects birds - but can also infect other animals, including horses, dogs, cats, bats, skunks, squirrels, chipmunks and domestic rabbits. Humans may also be infected.

The majority of infected humans often experience no signs or symptoms, while some may have just a skin rash and headache. A small proportion of infected individuals, however, may develop a life-threatening illness which may include encephalitis (inflammation of the brain), myelitis (inflammation of the spinal cord), or meningitis (inflammation of tissues surrounding the brain and spinal cord). Experts say approximately 1% of infected idividuals develop these serious complications. Those at highest risk for serious illness are the elderly and patients with lowered immune systems.

West Nile virus has three different possible effects on humans:

• Asymptomatic infection - there are no signs or symptoms. About 80% of cases.
• West Nile Fever (a mild febrile syndrome) - signs and symptoms are mild. Nearly 20% of cases.
• Neuroinvasive disease - the infection causes complications in the nervous system (brain and spine). About 1% of cases.

Source: Boston Public Health Commission

Written by Christian Nordqvist
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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