Epi news 11_wnv1.pdf

Summer 2003
EPI NEWS VOL. 3 NO. 3
A Publication of the Genesee County Health Department
West Nile Virus Update
WNV cases have been reported from Genesee County. The majority of human WNV cases this W the Middle East. It is a close relative year continue to arise from the Central U.S. of the St. Louis encephalitis virus and can infect Experts now believe that WNV will appear as a humans, birds, mosquitoes, horses and some seasonal epidemic in the U.S during the summer other mammals. The first domestically acquired cases of WNV encephalitis were documented in the U. S. in the summer of 1999. WNV spread throughout much of the U.S during 2000 and 2002. By the end of 2002, WNV activity had were documented, including, blood transfusion, been reported from 44 states and the District of organ transplantation, breast-feeding and trans- Columbia. In 2002, 4,156 human cases of WN placental transfer. WNV is not transmitted disease (including 2,942 meningo-encephalitis through casual contact. The incubation period cases and 284 deaths) were reported to the CDC. for WNV ranges from 3-14 days. Case-fatality Michigan was one of the worst hit States in the rate in the U. S. has been 7% overall, and 10% U.S during the 2002 WNV season, reporting the among patients with more significant WNV second highest number of WNV cases and deaths disease. Eighty percent of people who are bitten in the country. West Nile season started relatively late in the summer last year in infection, showing no symptoms of the illness Michigan. By the end of the season, over 2900 specimens were submitted for WNV testing to infection. Twenty percent of people will develop the Michigan Department of Community Health a mild form of the illness, called West Nile fever, (MDCH) laboratory. In 2002, there were a total with symptoms ranging from fever, headache, of 644 laboratory positive cases in Michigan, body and joint aches, fatigue, swollen lymph with 51 deaths that are attributable to WNV nodes, and rash. Less than 1% of those bitten by an infected mosquito will develop a more serious form of the disease, including those who develop threat for the third year in the U.S. As meningitis or encephalitis. Arboviruses have human cases of WNV infection and 134 deaths arthropods and birds or small mammals for their were reported from 43 states in the U.S. The survival. Birds are usually the preferred hosts for majority of WNV cases in the U.S. have been arboviruses; humans are generally a dead-end for reported from the State of Colorado, with 2090 (33% of all cases in the U.S) WNV cases and 38 deaths. So far this year in Michigan, only one The purpose of this quarterly newsletter is to inform the community and health care providers in Genesee County case of WNV has been reported this year. This about disease trends in the county. We welcome any Priya Nair, MPH, MSc, Epidemiologist, at should be drawn at least 22 days post onset. Treatment for WNV is supportive. Ribavirin in W clinical symptoms and patient history. high doses and interferon- 2b were shown to be Patients over 50 years of age with symptoms effective against the West Nile virus in vitro; such as fever, muscle weakness and severe however, controlled clinical trials have not been headaches and a travel history to areas (or residence) where West Nile virus activity has been identified have the highest risk of severe disease. These patients should be evaluated for WNV infection. IgM antibody testing of serum repellents containing DEET is very effective in specimens and cerebrospinal fluid (preferred test) protecting against mosquito bites. The American is the most efficient method of diagnosis. These Academy of Pediatrics and other experts suggest tests can be arranged through the Genesee that it is acceptable to apply repellent with low concentrations of DEET to infants over 2 months antibodies are produced very early in the infected old. Mosquito proofing homes by installing person. Consequently, the blood test may not be window and door screens and draining standing positive when symptoms first occur; however, water around homes is another way of reducing the test is positive in most infected people (90%) the risk of WNV. Dead birds are usually a sign that WNV is circulating between birds and antibody in cerebrospinal fluid strongly suggests mosquitoes in an area. The Genesee County central nervous system infection. Individuals Health Department (GCHD) is not collecting any who were recently vaccinated with yellow fever dead birds for WNV testing this year because or Japanese encephalitis vaccines or persons WNV is endemic in our area. County residents recently infected with a related flavivirus may are requested to submit dead bird reports to the have positive results on IgM antibody tests for www.michigandnr.com/wildlife/pubs/disease_ob antibodies in a single serum sample is not sreport.asp. The timely identification of human indicative of a recent infection with WNV. If cases of acute West Nile virus infections has serum specimens are used to make the diagnosis, important public health implications. Prompt paired acute and convalescent phase serum reporting of all cases of WNV to the GCHD will samples should be collected. The acute-phase enable a timely public health response to reduce specimen should be collected at least 8 days post the risk for additional human infections.
onset and the convalescent-phase specimen Selected Reportable Communicable Diseases in
Genesee County
Same week
Reported cases
Total reported
Week ending
reported cases to
FY* 2002-03
FY 2001-02
FY 2001-02
Chicken Pox
Pertussis
Flu-like illness
TB-New cases
Chlamydia
Gonorrhea
Hepatitis B (Acute)
Hepatitis C (Acute)
Campylobacter
Giardiasis
Hepatitis A
Salmonellosis
Shigellosis
Meningitis-Viral
Meningitis-Bacterial
*FY – Fiscal Year, October 1-September 30 Genesee County Health Department
Robert M. Pestronk, MPH, Health Officer • Gary K. Johnson, MD, MPH, Medical Director
630 S. Saginaw Street, Flint, MI 48502

Source: http://m.gchd.us/Newsletters/Epidemiology/EPI-Summer2003.pdf