More than 1,100 people in the U.S. have been infected with the West Nile virus and at least 41 people have died, making this year’s outbreak of the mosquito-carried virus the largest since 1999, when the virus was first detected in the U.S., according to the Centers for Disease Control (CDC).
Of the 1,118 cases nationwide, 34 are in California, the CDC reported. At least one person in California has died from the virus.
On Wednesday, a woman in Fontana was recovering from the first reported case of West Nile virus in San Bernardino County. It was not immediately known how or where she contracted it.
County officials have found the virus in 18 chickens and six mosquito samples, which is in line with last year’s figures, said Josh Dugas, with San Bernardino County Vector Control.
Extreme summer heat likely contributed to the spike in cases because the warm temperatures speed up the life cycle of the mosquito so it can go from an egg to a biting adult in five days.
The virus spreads by the bite of an infected mosquito, which has fed on an infected bird; and from mother to child during pregnancy or breast feeding, officials said. It can also spread during blood transfusions, transplants, though those instances are "very low," according to the CDC.
It cannot spread through casual contact and is not airborne.
Watch: How to Protect Against West Nile Virus
Most people infected with the virus, about 80 percent, will not show any symptoms, according to the CDC. Up to 20 percent of those infected will have symptoms such as fever, headache, body aches, nausea and vomiting, and swollen lymph glands or a skin rash.
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About one in 150 people infected will have to be hospitalized with severe symptoms, such as high fever, stupor, disorientation, tremors or muscle weakness.
People typically develop symptoms within three to 14 days of being bitten by an infected mosquito.
There is no specific treatment for the virus, which usually goes away with rest and increased fluid intake, officials said. Milder cases of West Nile virus will improve on their own and do not necessarily need medical attention, though some people may choose to see their doctors, the CDC reported.
If you develop severe symptoms, such as unusually severe headaches or confusion, the CDC advises you seek medical attention immediately.
With the unprecedented number of cases come warnings from health officials to take extra precautions against possible infection by wearing long-sleeved shirts and pants when outdoors and use mosquito repellent, especially at dawn and dusk.
Officials also urge eliminating and avoiding standing water where mosquitos can lay eggs. A Studio City woman pointed to a filthy swimming pool at a neighbor’s foreclosed home as the possible source for her case of the virus.
CDC: West Nile Virus Q&A
California’s 34 total cases were evenly split – 17 and 17 – between neuroinvasive, severe cases of the disease that affect a person’s nervous system, and nonneuroinvasive, less severe cases that do not show evidence of neuroinvasion, referred to as West Nile fever, the CDC reported.
The blood of 13 potential donors in California tested positive in preliminary tests when screen for the virus but showed no symptoms at the time they donated blood, according to the CDC.
Los Angeles County reported its first human case of the West Nile virus this year in July, when it was found in a middle-aged adult from San Gabriel Valley. LA County has reported five human cases of the virus so far, according to the LA County Department of Public Health.
LA County reported four fatal cases of the virus in 2011, one in 2009 and six in 2008, according to statistics from the LA County Department of Public Health. No fatal cases were reported in 2010, though four people were infected.
The 2012 outbreak has hit Texas the hardest, where 537 cases of the West Nile virus have been reported, 19 of them fatal, according to the CDC.
Those figures – significantly higher than the other 46 states that have reported cases – have prompted Texas officials to spray thousands of acres with insecticide, both on the ground and from the air.
Mississippi has the second-highest number of cases with 79, one of them fatal. Four states have reported more 65 cases within their borders.
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