High Number of Measles Cases Reported in US, CDC Says

Mark Crane

June 23, 2011

June 23, 2011 — The United States is experiencing the highest reported number of measles cases since 1996, most of which were acquired during international travel, the Centers for Disease Control and Prevention (CDC) said in an advisory sent to healthcare professionals yesterday.

From January 1 through June 17 this year, 156 confirmed cases of measles were reported to the CDC. Most cases (136) were associated with importations from measles-endemic countries or countries in which large outbreaks are occurring. The imported cases involved unvaccinated US residents who recently traveled abroad, unvaccinated visitors to the United States, and people linked to these imported cases.

To date, 12 outbreaks (3 or more linked cases) have occurred, accounting for 47% of the 156 cases. Of the total case-patients, 133 (85%) were unvaccinated or had undocumented vaccination status. Of the 139 case-patients who were US residents, 86 (62%) were unvaccinated, 30 (22%) had undocumented vaccination status, 11 (8%) had received 1 dose of measles-mumps-rubella (MMR) vaccine, 11 (8%) had received 2 MMR doses, and 1 (1%) had received 3 documented MMR doses.

Measles was declared eliminated in the United States in 2000 as a result of high 2-dose measles vaccine coverage, but it is still endemic or large outbreaks are occurring in countries in Europe (including France, the United Kingdom, Spain, and Switzerland), Africa, and Asia (including India).

The increase in measles cases and outbreaks in the United States this year underscores the ongoing risk for importations, the need for high measles vaccine coverage, and the importance of prompt and appropriate public health response to measles cases and outbreaks, the CDC advisory said.

Measles is a highly contagious, acute viral illness that is transmitted by contact with an infected person through coughing and sneezing. After an infected person leaves a location, the virus remains contagious for up to 2 hours on surfaces and in the air. Measles can cause severe health complications, including pneumonia, encephalitis, and death.

The CDC recommends that healthcare providers ensure that all patients are up to date on MMR vaccine and other vaccines. For those who travel abroad, the CDC recommends that all US residents older than 6 months be protected from measles and receive the MMR vaccine, if needed, before departure.

Infants aged 6 through 11 months should receive 1 dose of MMR vaccine before departure. Children aged 12 months or older should have documentation of 2 doses of MMR vaccine (separated by at least 28 days).

Teenagers and adults without evidence of measles immunity should have documentation of 2 appropriately spaced doses of MMR vaccine. One of the following is considered evidence of measles immunity for international travelers: birth before 1957, documented administration of 2 doses of live measles virus vaccine (MMR, MMRV, or measles vaccines), laboratory (serologic) proof of immunity, or documentation of physician-diagnosed measles.

Clinicians should consider measles as a diagnosis in anyone with a febrile rash illness lasting 3 days or more, a temperature of 101°F (38.3°C) or higher, and clinically compatible symptoms (cough, coryza, and/or conjunctivitis) who has recently traveled abroad or who has had contact with someone with a febrile rash illness. Immunocompromised patients may not exhibit rash or may exhibit an atypical rash. The incubation period for measles from exposure to fever is usually about 10 days (range, 7 - 12 days), and from exposure to rash onset is usually 14 days (range, 7 - 21 days).

Suspected measles case-patients should be isolated, and healthcare professionals should immediately report cases to local health departments to ensure a prompt public health response. Providers should obtain specimens for testing, including viral specimens for confirmation and genotyping, the CDC advises.

The CDC advisory updates data reported in the April 8 and May 27 issues of the CDC's Morbidity and Mortality Weekly Report.


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