West NileVirus: First Human Case of 2005

The CDC says the first reported case of human West Nile virus illness for 2005 is in Kansas.

No details were available on the patient's status.

West Nilevirus is transmitted seasonally by infected mosquitoes. Since 1999, when West Nile virus was first identified in the U.S., it has caused nearly 17,000 cases of human illness, including more than 650 deaths.

Though Kansas is the first state to report human West Nile virus activity this year, infection in birds, mosquitoes, or horses has already been reported from 14 states.

CDC: Take Precautions

"This season's first human case of West Nile virus reminds us of the importance of taking precautions to avoid becoming ill," says Lyle Petersen, MD, MPH, director of CDC's Division of Vector-Borne Infectious Diseases, in a news release.

"It's impossible to predict what this year's season will hold. So everyone who spends time outdoors should take steps to protect themselves from mosquito bites and West Nile virus," says Petersen.

Protection Strategies

The CDC recommends these simple measures to help prevent infection:

The CDC also encourages people to report dead birds to local health authorities to help with disease-monitoring activities.

Warding Off Mosquitoes

The CDC recently expanded the list of active ingredients it recommends for protection against mosquito bites.

In addition to DEET and permethrin, repellents containing picaridin and oil of lemon eucalyptus have recently been found to provide reliable and long-lasting protection from mosquito bites.

Higher-Risk Groups

West Nilevirus can be serious or even fatal, but a lot of people who get the virus don't get sick, says the CDC.

About two of every 10 people infected by a mosquito develop milder West Nile virus symptoms such as fever, aches, nausea, and vomiting. About one in 150 people infected with West Nile virus develop more serious symptoms.

Although people of any age can become severely ill, the risk is highest for people age 50 and over or people with weakened immune systems.

Virus Is Widespread

As of 2005, West Nile virus was reported in all states except Hawaii and Alaska. Washington state has reported only animal activity in one year, 2002.

West Nile "hot spots" -- places with high numbers of human cases -- have changed each year, but virus activity has generally continued locally each year after cases are reported, says the CDC.

In 2004, 2,535 human cases and 98 deaths were reported to the CDC, with the largest number of cases in Western states. Cases reported to CDC were highest in 2003, with 9,862 human illnesses and 264 deaths.

How West Nile Spreads

Mosquitoes become infected with West Nile virus when they feed on infected birds. The virus may be transmitted when an infected mosquito bites a human.

West Nilevirus transmission through transplanted organs, blood transfusion, and from mother to fetus and likely transmission to infants through breast milk were also identified in 2002.

Routine screening of blood donations for West Nile virus since 2003 has greatly reduced the risk of infection through blood transfusion, says the CDC.

By Miranda Hitti, reviewed by Michael W. Smith, MD

SOURCES: News release, CDC.