The California Department of Public Health (CDPH) reported yesterday the final human West Nile virus (WNV) numbers for 2014 and the tally is 801, more than double the number of cases seen by the state with the second most cases-Texas, which had 353 cases.


This is the most human WNV cases reported in the Golden State since 2005 when 880 cases were recorded (the most cases recorded in a single year).

  • The number of fatal WNV cases in 2014, 31, exceeded all previous years.

Health officials say the highest number of cases was in Orange County (263 cases) and the highest incidence occurred in Glenn County (35.3 cases per 100,000 population).

California Department of Public Health (CDPH) Director and State Health Officer Dr. Karen Smith said it is possible that the ongoing drought contributed to West Nile virus activity by creating more limited sources of water for birds and mosquitoes.

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

This is not the first time California reported the most WNV cases in the nation. Since reporting the first human case in 2002, California has topped the country in cases in 2004 (779), 2005 (880), 2008 (445), 2011 (158) and 2013 (379).

California has reported 4,806 total cases since 2002, only Colorado has reported more (In 2003 alone, Colorado reported 2,947 cases, the most cases seen in a state in a single year).

How does the West Nile situation in California look for 2015?

The CDPH says it is not possible to predict the level of WNV activity in 2015 because activity is influenced by many factors including climate, the number and types of birds and mosquitoes in an area, and the level of immunity in birds to WNV.

To date this year, West Nile virus activity has been reported in birds and mosquitoes in four counties–Alameda, Los Angeles, San Diego, and Santa Clara. There has not been a human WNV case seen so far.