As progress is made toward elimination of measles in the Americas, it will be critical to examine virus isolates from as many outbreaks and sporadic cases as possible for strain surveillance and to identify the source of the virus. From this standpoint, viral isolation is important. Automated DNA sequencing techniques are now available for rapid genetic characterization of viral isolates.
Virus isolation can take several days to weeks.
Therefore, IgM serology should always be the first priority in laboratory diagnosis of measles. Specimens for virus isolation should be taken at the same time that blood is obtained, since a delay in collection will reduce the chance of isolating the virus. Nasopharyngeal, or throat swab, or urine specimens should not be substituted for blood which is required for serologic diagnosis. Always collect a urine specimen and, if possible, attempt to collect a nasopharyngeal or throat specimen. Obtain the sample as soon as possible after onset of rash but no later than 4 days afterwards.