(CBS SF) — There were more than 800 human cases of West Nile virus throughout the state in 2014, the second-highest year on record to date, the state Department of Public Health announced Wednesday.
The state drought may be a contributing factor to last year’s spike in the virus, public health officials said.
“As birds and mosquitoes sought water, they came into closer contact and amplified the virus, particularly in urban areas,” state Public Health Director Dr. Karen Smith said in a statement.
“The lack of water could have caused some sources of water to stagnate, making the water sources more attractive for mosquitoes to lay eggs,” Smith said.
Santa Clara County had the most cases in the Bay Area last year, with the virus found in 10 people, 925 dead birds, and 30 mosquito samples, according to state data.
Alameda County had one human case and 96 dead birds that tested positive for the disease, according to the data.
Solano and Contra Costa counties each had five human cases of the virus, the data showed.
There were no human cases in Napa, San Mateo, Solano, or Sonoma counties. Those counties did have at least a dozen dead birds with the infection, according to the data.
Marin County also had no human cases, but did record six dead birds and three mosquito samples with the virus, public health officials said.
There were no reports of the virus in San Francisco and Monterey County, public health officials said.
Orange County had 263 human cases of the virus, the most among the 40 counties statewide that reported West Nile virus activity last year, public health officials said.
Los Angeles County came in second statewide with 253 cases among people, according to public health officials.
A total of 31 fatal cases occurred statewide last year, the highest number of deaths in a year from the disease to date.
Across the state, there was a record 561 cases of the neuroinvasive form of the disease that can lead to meningitis or encephalitis.
The virus entered the state in 2003 and the highest number of human cases recorded was 880 in 2005, public health officials said.
Higher temperatures can lead to a larger mosquito population, and unseasonably warm weather can mean an earlier season for West Nile virus, public health officials said.
West Nile virus season typically starts in the summer and there is a higher risk for the disease from mid-July through September.
Humans and animals can become infected by the bite of a mosquito with the disease, according to public health officials.
People are advised to apply insect repellent and wear protective clothing while outdoors to prevent mosquito bites.
The public is also advised to eliminate pools of standing water where mosquitoes tend to lay their eggs and replace any windows screens that have tears or holes.
Current information on West Nile virus activity can be found online at http://www.westnile.ca.gov.
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