In the most serious cases, infection can result in encephalitis, or swelling of the brain. Elderly individuals, or those with compromised immune systems, are most at risk. Health officials stress that there have been no known cases of illness caused by West Nile virus among humans this year, and these two birds are the only ones that have been positive of more than 125 tested since January. One hawk that died in February was confirmed positive at a Connecticut laboratory. Dead birds, especially crows, were present in large numbers in areas affected by last year's West Nile virus outbreak.
Crows are particularly susceptible to the virus, and the vast majority of infected crows die.
For that reason, they are considered to be an important early warning sign that infection could be present in a specific area. Birds are not the source of West Nile virus, but rather, serve as its reservoir, after being bitten by an infected mosquito. The Northern House Mosquito, or Culex pipiens, is the species most closely associated with transmission of West Nile virus. Those pools arrived at Wadsworth Laboratory yesterday to be tested for West Nile virus. Starting this week, the State laboratory began testing mosquito pools from counties in or near the area affected by West Nile virus last year.