The number of human West Nile virus (WNV) cases in California continue to mount as  Dr. Ron Chapman, director of the California Department of Public Health (CDPH) and state health officer said earlier this week, “We expect to see more people become infected as this is the time of year when the risk of infection is the highest.”

Orange County, California Image/David Benbennick
Orange County, California
Image/David Benbennick

California, as of Wednesday had the most cases in the US with 181 human cases of WNV from 22 counties, including eight fatalities so far in 2014.

No place in California has been hit harder by the mosquito borne virus than Orange County. As of Thursday, the Orange County Health Care Agency reported 91 total human WNV cases. These are broken down as follows: 61 West Nile neuroinvasive disease (the most serious form), 21 cases of West Nile fever and nine asymptomatic cases, infections detected at blood donation screening. There has been 3 fatalities reported.

According to the Centers for Disease Control and Prevention (CDC), approximately 80 percent of people (about 4 out of 5) who are infected with WNV will not show any symptoms at all.

Up to 20 percent of the people who become infected have symptoms such as fever, headache, and body aches, nausea, vomiting, and sometimes swollen lymph glands or a skin rash on the chest, stomach and back.Symptoms can last for as short as a few days, though even healthy people have become sick for several weeks. About one in 150 people infected with WNV will develop severe illness.

The severe symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness and paralysis. These symptoms may last several weeks, and neurological effects may be permanent.

Since first seen in the United States in 1999, over 37,000 WNV disease cases have been reported to the CDC, and this number likely underestimates the total number of infections. In addition to the human toll, an analysis published in the American Journal of Tropical Medicine and Hygiene (AJTMH) in February shows that hospitalized cases of WNV disease have cost a cumulative $778 million in health care expenditures and lost productivity over a 14 year period.

CDPH recommends that individuals prevent exposure to mosquito bites and West Nile virus by practicing the “Three Ds:”  DEET – Apply insect repellent containing DEET, picaradin, oil of lemon eucalyptus or IR3535 according to label instructions. Repellents keep the mosquitoes from biting you. DEET can be used safely on infants and children 2 months of age and older, DAWN AND DUSK – Mosquitoes bite in the early morning and evening so it is important to wear protective clothing and repellent if outside during these times. Make sure that your doors and windows have tight-fitting screens to keep out mosquitoes. Repair or replace screens with tears or holes and DRAIN – Mosquitoes lay their eggs on standing water. Eliminate all sources of standing water on your property, including flower pots, old car tires, and buckets. If you know of a swimming pool that is not being properly maintained, please contact your local mosquito and vector control agency.  For more infectiousdisease news and informationvisit and “like” the Infectious Disease News Facebook page