Karen Yates

Section for Communicable Disease Prevention

573-751-6113

West Nile Virus Cases Increasing In Missouri

The Missouri Department of Health and Senior Services (DHSS) announced today that cases of West Nile virus are on the rise. The health department also strongly encouraged Missourians to take extra precautions against infection over the Labor Day weekend.

As of August 28, 2003 Missouri has officially recorded five human cases of West Nile virus infection, four of which were verified within the past week. One case each has been reported in Putnam, St. Louis, and Jackson counties, and two cases have been reported from St. Louis City. One of the five cases died (an 82-year-old St. Louis City man). West Nile virus is currently considered to be at least a contributing factor in this death. A number of these investigations are ongoing and, therefore, these data are provisional and could change. Missouri had recorded 25 preliminarily positive West Nile virus cases by this time last year.

Human West Nile virus cases across the United States have risen sharply in recent weeks and currently stand at 1,442 cases from 34 states with 21 fatalities. A total of 480 cases were reported from 21 states and the District of Columbia for the same time in 2002.

The largest outbreak of West Nile virus human infection ever recorded worldwide occurred in the United States in 2002, when 4,156 cases were reported with 284 deaths. Missouri ranked eighth in number of cases (168); seven West Nile virus-related deaths were reported in Missouri last year.

“Although human cases of West Nile virus infection in Missouri are below last year’s levels, citizens should remain cautious,” said Dr. Howard Pue, state public health veterinarian. “West Nile virus is a late summer-early fall disease in humans. Nationwide, more than 75 percent of West Nile virus cases occurred during August and September last year. Missouri’s last case in 2002 became ill on October 12.”

DHSS, along with local public health agencies and other partners, conducts surveillance for West Nile virus infection in birds, mosquitoes, and horses. Results of this surveillance are used to determine the location and level of West Nile virus activity in the state and to thereby assess the public health risk. Activity was first detected in 2003 when a dead American Crow collected from St. Charles County on June 12subsequently tested positive for West Nile virus. Over the past week, the number of local public health agencies reporting West Nile virus activity increased from 42 to 48, and the number of dead birds that tested positive increased by almost 70 percent. Positive horses and mosquitoes also continue to increase.

Persons traveling to other states should be aware that there could be a significant risk of contracting West Nile virus at their destination. Other states are recording very high levels of activity. As of August 27, Colorado had reported 635 cases, South Dakota 204 cases, Nebraska 190 cases, and Texas 106 cases.

Although West Nile virus infection can result in a very serious disease, most infected people show no symptoms or develop a mild, flu-like disease. West Nile virus can affect all age groups, but it tends to be more serious in persons over 50 years of age. Approximately five to seven percent of those who develop signs of West Nile virus infection die from the disease.

Pue said that to prevent West Nile virus infection people should focus on personal protection and protection around the home. Avoid outdoor activity at dawn and dusk when mosquitoes are most active. Wear protective clothing such as pants and long-sleeved shirts. Apply insect repellents containing DEET to clothing and exposed skin; always follow label directions when applying repellents. Eliminate standing water from flowerpots, barrels, used tires, clogged gutters, and other places where mosquitoes can breed. Ensure doors and windows have screens that are in good repair. DHSS is collaborating with the Missouri Broadcasters Association to spread the prevention message through radio and television public service announcements to be aired over the next several weeks.

About half of Missouri’s cases last year became infected with West Nile virus around the Labor Day holiday weekend. Persons should take extra precautions, particularly as the weather cools and rainfall increases, which could promote breeding and other mosquito activity.

DHSS will continue to list new human cases on its West Nile virus web site. The privacy of infected individuals will be protected by the public release of limited demographic information -- the gender, age, and county of residence of each case. Only major developments in Missouri’s West Nile virus situation will be announced through news releases, including any deaths related to the virus. Human case data posted on the web site represent cases that are under investigation and are therefore provisional.

DHSS urges that physicians request analysis of specimens only from patients who currently show symptoms of West Nile virus infection. Because evidence of West Nile virus infection from last year can still be found in blood samples, a person’s symptoms play an important role in differentiating between cases of infection from last year and new infections this year. All human cases listed on the DHSS web site have been screened to eliminate the reporting of individuals who were infected in 2002.

For more information on mosquito-borne diseases, contact your local health department or DHSS at 1-866-628-9891. Additional information may be obtained by visiting DHSS’s web site at http://www.dhss.state.mo.us/WestNileVirus .