Measles is a highly infectious disease. Although it is no longer endemic in the U.S., an imported case can spread rapidly. Suspected measles cases should be immediately reported to MDH to facilitate case confirmation and ensure a rapid public health response. Case confirmation is based on clinical presentation, epidemiologic factors, and laboratory test results.
Measles may be tested by one or more of the following methods in order of preference:
● Detection of the virus by reverse transcription-polymerase chain reaction (RT-PCR)
● A positive viral culture for measles
● A positive measles-specific IgM antibody*(*False positive or negative results can occur and further interpretation or testing may be needed.
● A significant rise in IgG antibody between acute and convalescent paired sera (not commonly done).
Draw blood for IgM antibody testing as soon as possible. Occasionally, false negative measles with IgM results occur when blood specimens are collected within 72 hours after rash onset. A second blood sample, collected 72 hours after rash onset, should be tested in this situation.
Obtain acute and convalescent serum specimens for measles specific IgG antibody to confirm a measles diagnosis. Draw blood for acute IgG as early as possible when measles infection is suspected. For convenience, the blood draw for measles IgM antibody testing may be used for the acute IgG also.