MARBLEHEAD – Marblehead has its first reported case of West Nile Virus.Monday morning the Massachusetts Department of Public Health announced that a crow found in Marblehead tested positive for WNV, which is most commonly transmitted to humans by the bite of a mosquito infected with the virus.Director of Public Health Wayne Attridge said the bird was found in the West Ledge area off West Shore Drive.While the town has had birds that tested positive in the past, no birds tested positive for WNV in 2006 and the town made it almost all the way through summer this year without a report. In 2006, 4,261 dead birds were reported to the DPH and 57 tested positive for WNV.Behind the scenes, local health officials were keeping a vigilant eye on mosquitos, mosquito pools and dead birds, however. Attridge said he has met with the health agents in Salem and Swampscott “just about daily,” keeping an eye out for Eastern Equine Encephalitis as well as WNV.”We haven’t had any mosquito pools (in Marblehead) yet but I anticipate we’ll be finding one,” he said.Mosquito pools – stagnant water where mosquito larva can hatch and grow to maturity – can come in all sizes, and Attridge advised homeowners to either drain or get rid of items that hold water, like rain gutters and drains, unused flowerpots and wading pools, and changing water in birdbaths frequently.”There are two small ponds in that area of West Shore Drive, but people also have Koi pools, waterfalls and other water decorations,” he said, noting that water attracts sick birds as well as mosquitos.”It’s the simple things like that that we overlook,” he said.He also advised people going out in the evening to put on mosquito repellent, including youths attending athletic practices.Dead crows, blue jays or robins may be a sign of WNV in an area. Residents may call 1-866-MASS WNV to report a dead bird.