West Nile virus tracking and monitoring season is underway and an updated online dead bird reporting system is available for state residents to use.  Dead birds can be the first sign that West Nile virus is circulating in an area.   Don Moyer, spokesman for the Washington State Department of Health says, "dead birds are often an indicator of where West Nile virus may be present, West Nile virus is a bird disease that is transmitted by mosquitos, so if you get a number of dead birds in a certain area, it's worth taking a lot at that area, so residents can take steps to try and avoid mosquito bites."   The Centers for Disease Control and Prevention has just released final data from the 2012 season, with 5,764 cases of West Nile virus disease in 48 states (excluding Hawaii and Alaska).  In Washington state two people contracted the virus, one in Yakima County, another in Benton County.  Avoiding mosquito bites is the key to preventing West Nile virus.  West Nile virus can cause illness in people, birds, horses and other mammals if bitten by an infected mosquito.  Washington residents may report dead birds online now through October.  You can report dead birds at www.doh.wa.gov.