The number of human West Nile virus (WNV) cases increased by 65 during the past week, bringing the state’s total to 375, far higher than any other state in the country.

Culex mosquito
Culex quinquefasciatus

The 375 WNV cases so far in 2014 is double 2013 numbers and significantly higher thean the 5-year average of 95 cases.

The increase in the mosquito borne viral disease is in part due to the serious drought California is experiencing this year. “When we have less water, birds and mosquitoes are seeking out the same water sources, and therefore are more likely to come in to closer proximity to one another, thus amplifying the virus,” says Vicki Kramer, chief of vector-borne diseases at the state Department of Public Health.

The new cases were reported from the following counties: Butte (3), Fresno (1), Glenn (1), Kern (1), Los Angeles (19), Madera (1), Orange (23), Riverside (3), Sacramento (3), San Bernardino (1), San Joaquin (1), Stanislaus (3), Tehama (1), Tulare (1), Yolo (2), and Yuba (1).

Orange County has reported 139 cases to date, double the number of cases from any other county. Los Angeles County is second with 69.

15 WNV-related fatalities have been reported in to CDPH from in eight local health jurisdictions: Glenn (1), Long Beach City (1), Los Angeles (2), Orange (4), Sacramento (2), Shasta (1), Stanislaus (2), and Sutter (2).

According to the Centers for Disease Control and Prevention (CDC), as of September 16, a total of 45 states and the District of Columbia have reported West Nile virus infections in people, birds, or mosquitoes. Overall, 725 cases of West Nile virus disease in people have been reported to CDC, including 25 fatalities. This number will be updated by the CDC later today. For more infectious disease news and information, visit and “like” the Infectious Disease News Facebook page