West Nile Virus Kills 15 In U.S., Says CDC

The CDC reported Thursday that that so far this year, West Nile virus has sickened 444 people in the U.S., including 15 people who died of West Nile virus illness.

Those figures, published in the CDC's Morbidity and Mortality Weekly Report, include West Nile cases reported to the CDC as of Aug. 14.

Five of the West Nile virus deaths occurred in California. South Dakota reported two deaths from West Nile virus. Alabama, Arkansas, Colorado, Illinois, Mississippi, North Dakota, Oklahoma, and Wyoming each reported one West Nile death.

Overall, 27 states have reported human cases of West Nile virus as of August. Western states led the list. California reported 86 cases — more than any other state. Other states with high numbers of West Nile cases included Colorado (72 cases), South Dakota (62 cases), North Dakota (52 cases), and Wyoming (34 cases). Those illnesses began between March 25 and Aug. 5, according to the CDC.

Last year, the CDC had reports of 388 people in the U.S. who were sickened by West Nile virus by the middle of August, including 13 people who died of West Nile virus illness.

Though this year's numbers are higher than those from the same time last year, it's too soon to know whether the figures reflect a true rise in West Nile virus cases, since state reports may not be complete, CDC spokeswoman Christine Pearson tells WebMD.

West Nile virus typically flares up in the summer and continues into the fall. That's prime time for mosquitoes, which can transmit West Nile virus.

West Nile virus can also spread through blood transfusions, organ transplants, breastfeeding, and from mother to baby during pregnancy — but those cases have been rare, according to the CDC.

Most people infected with West Nile virus don't get sick. The CDC estimates that about one in five people who get infected with West Nile virus develop mild symptoms such as fever, headache, body ache, nausea, vomiting, and sometimes swollen lymph glands or skin rash on the chest, stomach, and back. Symptoms may last for a few days to a several weeks.

About one in 150 people infected with West Nile virus develop severe illness. Their symptoms can include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, vision loss, numbness, and paralysis. Those symptoms may last for several weeks, and neurological effects may be permanent, according to the CDC.

Here are the CDC's tips to prevent West Nile virus infection: