|CA Dept. of Public Health||UC Davis Arbovirus Research and Training||Mosquito and Vector Control Assoc. of CA|
Case Counts by County
2020 | 2019 | 2018
2017 | 2016 | 2015
2014 | 2013 | 2012
2011 | 2010 | 2009
2008 | 2007
California Sets Record for West Nile Virus ActivityApr 8, 2015
It is possible that the ongoing drought contributed to West Nile virus activity by creating more limited sources of water for birds and mosquitoes, according to Dr. Smith.
"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.
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.
As the weather warms up, mosquitoes become more abundant. Unseasonably warm weather this year could lead to increased mosquito abundance and promote an early start to the WNV disease season. The WNV season typically begins in the summer and tapers off in the fall months, with the highest risk for disease occurring in mid-July through September.
West Nile virus is transmitted to humans and animals by the bite of an infected mosquito. For most people, the risk of serious illness is low. However, some individuals - less than one percent - can develop a serious neurologic illness, such as encephalitis or meningitis. People 50 years of age or older and people with diabetes and/or high blood pressure have the greatest risk of developing serious complications.
CDPH recommends that individuals prevent exposure to mosquito bites and West Nile virus by practicing the "Three Ds:"
California's West Nile virus website includes the latest information on West Nile virus activity in the state. Californians are encouraged to report all dead birds through the website. Starting April 15, dead birds can be reported by calling toll-free 1-877-WNV-BIRD (968-2473).
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Compared to previous year and previous five-year average to date