BOSTON (AP) - West Nile virus killed a bird found dead in a city park, making Massachusetts the fifth state where the virus has spread since it was detected in North America a year ago, health officials said.
A state laboratory confirmed it was West Nile virus Wednesday.
City officials said they would begin spraying pesticides on public land to kill mosquitoes, which can transmit the virus to humans. Officials also pledged to increase statewide monitoring for the virus.
An extensive effort to combat the West Nile virus is already under way in New York, where an outbreak last year killed seven people. The virus also has been found in New Jersey, Connecticut and Maryland.
This year, no human cases have been found in New York. But the virus continues to show up in birds and insects. On Monday, Central Park was closed overnight so insecticides could be sprayed.
The West Nile virus can cause encephalitis, a dangerous swelling of the brain which can be deadly. Most who contract it experience flu-like symptoms, and may not know they have it.
Massachusetts officials cautioned that the discovery there was expected and that there had been no cases of the virus occurring in humans.
''This is no cause for alarm, or any reason to change vacations, or not go outside, or not let your children go outside,'' said Dr. Stephen Zinner, a Harvard Medical School professor. ''In this area, we are used to protecting ourselves from mosquito bites because of Lyme disease.''