West Nile Cases Triple in One Week

Virus Quickly Spreading Westward, Worst May Be Yet to Come

From the WebMD Archives

Aug. 7, 2003 -- This year's West Nile virus outbreak is already outpacing last year's and showing some disturbing new trends that have health officials reaching for the mosquito repellent.

According to the CDC, the number of people infected with the West Nile virus has more than tripled in the last week alone to at least 164 people in 16 states compared to only 112 cases in four states that were reported at this time in 2002. So far this year, the CDC attributes four deaths to the virus.

"The bottom line is that it's here, it's happening in a lot of jurisdictions, every sign indicates that it's on the increase, and now is the time to for people to step up their efforts to fight the bite," says CDC Director Julie Gerberding in a telebriefing today.

Gerberding says that so far all 164 West Nile cases have been attributed to mosquito bites, and the disease does not appear to be spreading through other means. The CDC recently began screening the blood supply for the West Nile virus to prevent transmission of the virus through infected blood.

Disturbing New Trends

Aside from outpacing last year's outbreak, officials say the West Nile virus also appears to be acting in some other troubling new ways.

In previous years, the virus primarily affected older people and caused the most serious illness in senior citizens. So far this year, the average age of Americans infected with the West Nile virus is 45 compared to 55 in last year's outbreak.

Gerberding says it's too early to draw conclusions about the age of West Nile victims, and that change might be due to better reporting of milder cases of West Nile illness among younger people.

The West Nile virus causes two types of illnesses in humans: brain swelling disorders known as encephalitis or meningitis that are responsible for most of the deaths attributed to the virus, and a less serious flu-like West Nile fever that may not require hospitalization.

Virus Spreading Westward

The first U.S. cases of West Nile virus in humans were discovered in the Northeast in 1999 but since then the virus has quickly spread across the country. Last year, several states in the Midwest and South were among those hardest hit by the virus, and now the virus appears to be spreading westward.


For example, last year at this time Colorado had yet to report a single case of West Nile virus infection in humans. But this year, Colorado has reported nearly four times as many cases of West Nile virus infection in humans than any other state with at least 72 reported cases, including at least one death. Texas has had the second highest number of cases with 29 cases so far and at least two deaths. Alabama makes up the last of the states to have a West Nile virus death reported so far this year.

Gerberding says that state agencies may have more up-to-date figures on the numbers of cases and deaths from West Nile virus and that the CDC's numbers will be updated as more confirmed reports come in.

According to the CDC, cases of West Nile virus infection in humans have currently been reported in Alabama, Colorado, Florida, Iowa, Kansas, Kentucky, Louisiana, Minnesota, Mississippi, Nebraska, New Mexico, North Dakota, Ohio, South Carolina, South Dakota and Texas. Reports of new cases in other states, including Georgia, are also currently being investigated.

In 2002, there were 4,156 reported cases and 284 deaths in the U.S. due to illness caused by the West Nile virus.

How to Protect Yourself from West Nile Virus

Officials say now is the time for the public to protect themselves from becoming infected with the West Nile virus. Last year, there was a large spike in West Nile cases in the second week of August, and 65% of the cases that occurred in the entire season occurred in the following six weeks.

"We are starting the epidemic with more cases and more areas affected than last year and if the same pattern proves to hold true we could be seeing an even greater number of affected people," says Gerberding. "The time for people to really be conscientious about taking the steps necessary to protect themselves from mosquito bites is right now and to continue those activities throughout the rest of the summer season."

Those steps include:

  • Use an insect repellent with DEET when outdoors in areas where there are mosquitoes.
  • Wear long sleeves, long pants and socks whenever possible outdoors. Mosquitoes may bite through thin clothing so spraying clothing with insect repellent can offer additional protection.
  • Be aware of peak mosquito hours (dusk to dawn) and take extra precautions during these times.
  • Mosquito-proof your home by using screens on windows and emptying any items on the property that hold standing water where mosquitoes can breed, like birdbaths, flower pots, old tires, cans and clogged rain gutters.
WebMD Health News Reviewed by Michael W. Smith, MD on August 07, 2003


SOURCES: CDC Telebriefing, Aug. 7, 2003. WebMD Special Report: "West Nile Virus".

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