High Number of Reported Measles Cases in the U.S. in 2011—Linked to Outbreaks Abroad

Distributed via the CDC Health Alert Network
June 22, 2011, (4:00 PM EST)
CDCHAN-00323-11-06-22-ADV-N

Summary and Background

The United States is experiencing a high number of reported measles cases in 2011, many of which were acquired during international travel. From January 1 through June 17 this year, 156 confirmed cases of measles were reported to CDC. This is the highest reported number since 1996. Most cases (136) were associated with importations from measles-endemic countries or countries where large outbreaks are occurring. The imported cases involved unvaccinated U.S. 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 U.S. 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 doses, and 1 (1%) had received 3 (documented) doses.

Measles was declared eliminated in the United States in 2000 due to our 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 of importations, the need for high measles vaccine coverage, and the importance of prompt and appropriate public health response to measles cases and outbreaks.

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.

Recommendations for Health Care Providers

• Ensure all patients are up to date on MMR vaccine* and other vaccines.
• For those who travel abroad, CDC recommends that all U.S. residents older than 6 months be protected from measles and receive MMR vaccine, if needed, prior to departure.
  • Infants 6 through 11 months old should receive 1 dose of MMR vaccine before departure.†
  • Children 12 months of age 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.
• Consider measles as a diagnosis in anyone with a febrile rash illness lasting 3 days or more, a temperature of 101ºF (38.3ºC) 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 to 12 days) and from exposure to rash onset is usually 14 days (range, 7 to 21 days).
• Isolate suspect measles case-patients and immediately report cases to local health departments to ensure a prompt public health response.
• Obtain specimens for testing, including viral specimens for confirmation and genotyping.

* Children 1 through 12 years of age may receive MMRV vaccine for protection against measles, mumps, rubella, and varicella; however, MMRV vaccine is currently unavailable.

† Infants who receive a dose of MMR vaccine before their first birthday should receive 2 more doses of MMR vaccine, the first of which should be administered when the child is 12 through 15 months of age and the second at least 28 days later.

** One of the following is considered evidence of measles immunity for international travelers: 1) birth before 1957, 2) documented administration of 2 doses of live measles virus vaccine (MMR, MMRV, or measles vaccines), 3) laboratory (serologic) proof of immunity, or 4) documentation of physician-diagnosed measles.

For more information:

• CDC. Measles among Unvaccinated U.S. Residents Aged 6–23 Months Who Have Traveled Outside the United States, 2001–2011. MMWR. 2011;60:397–400.
• CDC. Measles–United States, January–May 20, 2011. MMWR. 2011;60;666–8.
• CDC. Notes from the Field: Measles Outbreak–Hennepin County, Minnesota, February–March 2011. MMWR. 2011;60:421.
• CDC’s Measles (Rubeola) website
• CDC’s Measles Vaccination website
• Medscape Today: CDC Expert Commentary: Measles: What You Might Not Know Recognizing, diagnosing, and preventing measles (running time: 5:20 mins)