As of Tuesday, a total of 118 fatalities have been blamed on West Nile virus infections since the beginning of the year, up from 87 on September 2, the Centres for Disease Control and Prevention said. The number of cases rose to 2,636 from 1,993 during the same time frame, a 32 per cent increase.
"The 2,636 cases reported thus far in 2012 is the highest number of West Nile virus disease cases reported to CDC through the second week in September since 2003," the agency said on its website.
The virus was first detected in the United States in 1993. This year could see a record of cases deemed neuroinvasive, or capable of penetrating the central nervous system – currently 1,405, or 53 per cent, are classified as such.
Two thirds of the cases have been reported from six states – Texas, Louisiana, South Dakota, Mississippi, Michigan and Oklahoma. Forty per cent of all cases are concentrated in Texas, according to the CDC.
The soaring number could be due to a relatively mild winter, an early spring and hot summer.
Other factors potentially contributing to the outbreak are birds transporting the virus and the exploding mosquito population.
First identified in Uganda in 1937, the virus manifests itself in a number of different ways and 80 per cent of the time does not spark serious symptoms.
However, it can also cause potentially fatal complications such as meningitis or encephalitis.