Reporting & Investigation of West Nile Virus

Table of Contents

A. Purpose of Surveillance and Reporting

  • To identify locally acquired cases of WNV infection in humans to help target mosquito control measures.

  • To identify cases of other arboviral infections in Iowa residents or visitors to determine whether they are imported or locally acquired.

  • To identify cases of WNV infection to understand the epidemiology of this emerging disease in our area.
  • To provide residents of Iowa and travelers to the state with appropriate preventive health information.

B. Laboratory and Healthcare Provider Reporting Requirements 

Iowa Administrative Code 641-1.3(139) stipulates that the laboratory and the healthcare provider must report. The preferred method of reporting is by utilizing the Iowa Disease Surveillance System (IDSS).  However, if IDSS is not available, the reporting number for IDPH Center for Acute Disease Epidemiology (CADE) is (800) 362-2736; fax number (515) 281-5698, mailing address:

Iowa Department of Public Health, CADE
Lucas State Office Building, 5th Floor
321 E. 12th St.
Des Moines, IA 50319-0075

Postage-paid disease reporting forms are available free of charge from the IDPH clearinghouse. Call (319) 398-5133 or visit the website: healthclrhouse.drugfreeinfo.org/cart.php?target=category&category_id=295 to request a supply.

Laboratory Testing Services Available

The University of Iowa State Hygienic Laboratory (SHL) performs antibody detection for West Nile virus using enzyme immunoassay (EIA) methods. Single acute sera and cerebrospinal fluid (CSF) are tested for the presence of IgM antibodies. WNV antibodies develop soon after onset and peak around 8 days, therefore, sera and CSF collected 5-10 days post onset are ideal specimens for testing. The presence of IgM antibody usually indicates recent infection by this virus; however, it has been shown that IgM antibodies to WNV may persist for many months after onset. IgG testing is not routinely done.  Confirmatory testing, if indicated, is performed at the CDC. Accurate information about date of specimen collection, date of onset of symptoms, travel history, vaccination and disease history are helpful for test result interpretation. For information on specimen submission and testing, contact SHL at (319) 335-4500. Additional information, test request forms, and sample collection instructions can be found at the SHL web site at: www.shl.uiowa.edu/

C. Local Public Health Agency Follow-Up Responsibilities

Case Investigation

The local public health agency (LPHA) should follow-up on reported cases of WNV.

  • Neuroinvasive disease includes diagnoses of West Nile encephalitis, West Nile meningitis or West Nile meningoencephalitis, neuritis/neuropathies, or myelitis. The severe WNV illnesses typically require hospitalization. The LPHA should work with the infection preventionist (IP) at the hospital to complete the WNV case investigation in IDSS.
  • Non-neuroinvasive disease includes WNV Fever and any other diagnoses of WNV including symptoms consistent with the illness and/or clinically apparent disease not involving encephalitis, meningitis or meningoencephalitis (neurological involvement).  LPHA will complete the investigation for WNV.
  • Asymptomatic test positives include individuals who have been infected with and tested positive for WNV without becoming ill (remaining asymptomatic or without clinically apparent disease). Please note in IDSS if this is the situation.

If  several attempts have been made to obtain case information, but have been unsuccessful (e.g., the case or healthcare provider does not return calls or respond to a letter, or the case refuses to divulge information or is too ill to be interviewed), complete the investigation with as much information as has been gathered. Please note the reason why it could not be completed. If using IDSS, select the appropriate reason under the Event tab in the Event Exception field.