California West Nile virus activity breaks records in 2014

West Nile virus activity breaks records in California last year.
West Nile virus activity breaks records in California last year. | Courtesy of
A report from the California Department of Public Health (CDPH), released on Wednesday, said the state saw record highs for West Nile virus (WNV) activity last year.

This is the first time that California has experienced such high WNV rates since WNV first entered the state in 2003. In 2014, there were 801 WNV cases, the second-highest number of human WNV cases for the state; in 2005, there were 880 cases.

Orange County saw 263 WNV cases in 2014, the highest number in the state. Glenn County currently had the highest incidence rate of WNV based on population, with 3.53 cases for every 100,000 people.

2014 broke a number of records for WNV activity in California, with 561 cases of West Nile neuro-invasive diseases (WNND) confirmed, and 31 people dying from WNV, both highs. Mosquitoes registered a record-breaking level of WNV infection rates, and 60 percent of dead birds tested positive for WNV infections.

State Health Officer Dr. Karen Smith said the ongoing drought in California has contributed to the high activity rates of WNV in the state because there are very limited water sources for mosquitoes and birds.

“As birds and mosquitoes sought water, they came into closer contact and amplified the virus, particularly in urban areas," Smith said. "The lack of water could have caused some sources of water to stagnate, making the water sources more attractive for mosquitoes to lay eggs.”

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California Department of Public Health

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