Six mosquito samples collected last week have tested positive for West Nile virus in Suffolk County, tripling the case number reported for the season, health officials said Thursday.

Two positive samples were collected July 20 in Selden and one each that same day in West Babylon, West Islip, Holbrook and Southold. To date this season, nine mosquito samples have tested positive for West Nile in Suffolk, officials said.

"The confirmation of West Nile virus in mosquito samples indicates the presence of West Nile virus in the area," said Suffolk Health Commissioner Dr. Gregson Pigott. "While there is no cause for alarm, we advise residents to cooperate with us in our efforts to reduce exposure to West Nile virus and other mosquito-borne diseases."

Mosquito samples collected July 6 in Nesconset and July 8 in Northport and July 14 in Holbrook previously tested positive for the virus, Pigott said

West Nile, which was first detected in Suffolk in 1999, is transmitted to humans by the bite of an infected mosquito.

While most people who contract the virus have mild or no symptoms, West Nile can cause severe symptoms such as muscle weakness, vision loss and neurological problems, which in some people are permanent. The symptoms, which can be more severe among those 50 and older and those with compromised immune systems, may last several weeks.

To prevent West Nile, containers holding water, such as buckets, pet water bowls, birdbaths, and trash cans should be emptied weekly and scrubbed to prevent the growth of mosquitoes, Pigott said.

He also urged residents to minimize outdoor activities between dusk and dawn, wear long pants, long-sleeved shirts and shoes and socks when mosquitoes are active, use mosquito repellent, and make sure all windows and doors have intact screens.

Residents can report mosquito problems or stagnant pools of water by calling 631-852-4270. If you see a dead bird — which could indicate the presence of the West Nile virus — take a photograph of the bird and call 631-852-5999 between 9 a.m. and 4 p.m.

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