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Travel-related importation factors heavily into recent measles outbreaks

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200 of 222 measles cases reported to CDC in 2011 were linked to importation by people visiting the United States or Americans who traveled abroad and brought back the virus.

A total of 222 Americans were reported to have measles in 2011—the highest number of reported cases in the United States in the past 15 years, according to CDC. Of the 222 cases, 200 were associated with importation, either by people from other countries visiting the United States or U.S. residents traveling abroad and bringing back the virus. Seventeen measles outbreaks occurred last year, which CDC said was four times the usual number.

The agency's findings are published in a report, Measles — United States, 2011, in the April 20 Morbidity and Mortality Weekly Report. During a telebriefing yesterday, Anne Schuchat, MD, from the CDC National Center for Immunization and Respiratory Diseases, discussed two key topics related to last year's measles activity: the influence of travel importation and the importance of vaccination, particularly among children and other at-risk patient populations.

Travel-associated measles importation

Because of high immunization rates for measles in the United States, CDC declared the disease eliminated in 2000, following interruption of the transfer of disease from person to person. However, the 222 measles cases and 17 outbreaks in 2011 reported to CDC from 31 different states were the most since 1996, during which 508 cases occurred. Schuchat said that between 2001 and 2010, a median of 60 cases of measles were seen each year.

On a worldwide level, however, measles is much more prevalent; globally, 20 million people get measles each year. The virus can be easily imported by travelers visiting the United States or Americans who acquire measles during travel abroad and bring it back.

"Measles can be serious—even in developed countries like the United States," said Schuchat. "For every 1,000 children who get measles, between 1 and 3 might die from the infection, despite very good treatment."

Measles is extremely contagious and can be spread easily through coughs and sneezes. "You could catch measles just by being in the room where a person with measles has been, even after that person has left the room," noted Schuchat.

In 2011, 72 actual cases of measles importation occurred; nearly half were from the European region. "Recently, there has been a lot of measles in Europe," said Schuchat. "In 2011, more than 37,000 measles cases were reported from Europe, and some of the countries that have been hardest hit are places that Americans frequently travel, like France, Italy, and Spain."

Pharmacists play a key role in helping to ensure that Americans traveling abroad are up to date on their immunizations and receive appropriate vaccinations based on the characteristics of the places to which they are traveling and their specific itineraries.

Children and other susceptible people

More than 90% of children in the United States have been vaccinated against measles. However, explained Schuchat, "measles is extremely infectious and it's very good as a virus at finding those people who are not immunized or protected."

Most (86%) of the measles cases in 2011 were among individuals who were not vaccinated (65%) or did not know whether they were vaccinated (21%; mostly adults).

Of the 166 U.S. residents who were unvaccinated or had unknown vaccination status, 141 (85%) were eligible to get the MMR (measles–mumps–rubella) vaccine. And of those 141 individuals, 66 were aged 16 months to 19 years—a range during which they should have already received the vaccine and when school or daycare requirements could have served as good reminders to get the vaccine. Among those 66 cases, 50 (76%) involved patients having a philosophical objection or religious or personal belief exemption to vaccination, reported CDC.

The MMR vaccine is recommended in two doses: the first at 12 through 15 months of age and the second at age 4 to 6 years. However, CDC stated the second dose can be given earlier, as long as it's 28 days after the first dose.

The agency also recommends that unless evidence of immunity to measles exists, college and other students, health care workers, and anyone traveling internationally should have two appropriately timed doses of the MMR vaccine. CDC also advises that if children older than 6 months are traveling abroad, they should receive the vaccine early instead of at the 12-month, normally recommended time point.

The 'continuing story'

"Each case of measles requires a rapid, intensive investigation, to make sure measles doesn't take hold again in the United States," said Schuchat. She added that the measles outbreaks during 2011 remained small and contained as a result of high vaccination rates and a vigorous public health response from state and local health departments.

The "continuing story," said Schuchat, is that measles cases are still being seen in 2012, with more than 25 cases reported thus far, most of which have been associated with importation.

The importance of vaccinating children against measles dovetails perfectly with National Infant Immunization Week (NIIW), which is this coming week (April 21–28). NIIW is a celebration of the successes provided by vaccines and the critical need to protect children through immunization.

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