The US Centers for the Disease Control and Prevention (CDC) today sounded an alarm that measles cases have reached a 20-year high for this point of the year, with much of the spike driven by unvaccinated travelers who brought the disease back from international destinations.

With its warning, the CDC urged people to get vaccinated as the summer travel season approaches.

At a media briefing today, Anne Schuchat, MD, director of the CDC's National Center for Immunization and Respiratory Diseases, said the surge in measles cases is a wake-up call for parents to make sure their children's vaccinations are up to date. Since the first of the year through May 23, the CDC has received reports of 288 cases in 18 states.

Schuchat said 138 of the cases are linked to an ongoing outbreak centered in Ohio's Amish communities, which seems to be fueled by unvaccinated adults participating in service projects in the Philippines, where a massive measles outbreak has sickened more than 32,000 this year.

Yesterday the Ohio Department of Health (ODH) said it has recorded 160 measles cases so far and has distributed more than 13,000 doses of vaccine to battle the outbreak. It added that local health departments have administered 8,240 doses so far.

Schuchat said nearly all US measles cases have been imported from other countries, and health officials have traced those connections to 18 different countries.

Fifteen outbreaks have been reported, and other hot spots include New York City and California, where six outbreaks have been reported in six different counties.

Unvaccinated serve as 'welcome wagon'

Ninety percent of people who were sickened by the virus hadn't received the vaccine or didn't know their vaccination status, according to the CDC. Of US residents in that group, 85% were unvaccinated because of religious, philosophical, or personal reasons.

As one of the most contagious diseases, measles spreads easily among unvaccinated people, and several of the outbreaks this year have occurred in pockets of unvaccinated people, Schuchat said.

"Measles is coming in on airplanes from places where the disease still circulates or where large outbreaks are occurring," she said. "Imported measles virus is landing in places in the US where groups of unimmunized people live. That setting gives the measles virus a welcome wagon."

So far the measles has put 43 patients (15%) in the hospital, but no deaths have been reported, she said. Patient ages range from 2 months to 65 years, though more than half of the infections have been in adults 20 or older.

In a report today in Morbidity and Mortality Weekly Report (MMWR), CDC experts said the number of cases reported this year so far has passed the highest total of yearly cases since the disease was eliminated in 2000. In all of 2011, 220 cases were reported, which had been the post-2000 high.

The experts urged health providers to keep a high index of suspicion for measles in patients with fever and rash, and noted that some cases were initially misdiagnosed as Kawasaki disease, dengue infection, and scarlet fever.

Also, the CDC urged health providers to remind patients who plan on international travel, including large gatherings such as the World Cup in Brazil, to be vaccinated, and that anyone age 6 months and older who hasn't been immunized should receive the vaccine.

See also:

May 29 CDC press release

May 28 ODH statement

May 29 MMWR report