The Massachusetts Department of Public Health (DPH) has raised the risk level for West Nile virus from low to moderate statewide, a move it has made only once before. A little less than half of the state’s 351 cities and towns were already considered at moderate risk, with the remainder at low risk. There have been no reported human cases of West Nile virus to date in Massachusetts.
State officials posted the announcement Aug. 21. On the same day, the Nashoba Associated Boards of Health sent an advisory letter to all towns in the Nashoba Health District, including Harvard, to notify them that mosquitoes infected with West Nile virus had been found in the district. Earlier this month, testing conducted by the Central Massachusetts Mosquito Control Project detected two mosquitoes carrying the virus in neighboring Devens, and, to reduce the threat, began treating the areas where the infected mosquitoes were found.
State public health commissioner Monica Bharel cited the recent hot, humid weather coupled with frequent heavy rains as providing “perfect conditions for mosquito species carrying West Nile virus to breed.” In a DPH press release, Bharel said, “I strongly encourage everyone to keep using insect repellent and to be especially aware of mosquito activity at dusk and dawn when the risk of being bitten by mosquitoes is greatest. Move indoors if you are getting bitten.”
According to the Centers for Disease Control and Prevention, about one in five people who are bitten by a mosquito carrying West Nile virus may develop flu-like symptoms, including fever, and the rest generally have no symptoms. But about one in 150 develops a severe illness affecting the central nervous system, and people older than 50 are at higher risk for such an illness.
To avoid mosquito bites, the DPH recommends using repellents with Deet, permethrin, picaridin, or oil of lemon eucalyptus. It also recommends wearing long sleeves, long pants, and socks when outdoors, and staying indoors during peak mosquito hours (dusk and dawn). Holes in screens in doors and windows should be repaired to keep mosquitoes out.
Because mosquitoes lay their eggs in standing water, residents are advised to eliminate sources of standing water in yards, such as empty flower pots or wading pools. Horse owners should flush out water troughs at least once a week, and horses should be kept in indoor stalls at night since they are also susceptible to West Nile virus.
More information can be found on the state’s Arbovirus Surveillance Information web page at www.mass.gov/dph/mosquito as well as Harvard’s Board of Health mosquito web page at www.harvard.ma.us/board-health/pages/mosquitoes.
