Measles cases in the United States hit a 15-year high in 2011, with 90% of the cases traced to other countries with lower immunisation rates, the Centres for Disease Control and Prevention reported in the Morbidity and Mortality Weekly Report (MMWR).
There were 222 cases of measles in the United States last year, more than triple the usual number, the agency said. There had been only about 60 cases per year between 2001 and 2010.
No one has died of the disease in the United States since 2008. But approximately 20 million people contract the measles virus each year worldwide, and about 164,000 die from it, said Dr Anne Schuchat, director of the health agency's National Centre for Immunisation and Respiratory Diseases.
The agency said in 2000 that home-grown measles had been eliminated, but cases continued to arrive in the United States from abroad.
Immunisation lower in Europe than US
There have been more than 25 measles cases reported so far in 2012, most of them imported, the CDC said.
Measles cases were found in 31 states in 2011. Last year's count marked the highest number of cases since 1996, when there were 508 cases in the United States.
All but 22 of the 222 cases last year involved patients who had been infected overseas or caught the virus from someone who had been abroad, the CDC said. The source of the other 22 cases could not be determined.
Many of the cases were traced to Europe; where in some countries' immunisation rates are lower than in the United States. Europe suffered an outbreak of the disease in 2011, reporting more than 37,000 measles cases.
France, Italy and Spain, popular destinations for US tourists, were among the hardest hit, said Dr Schuchat.
Measles is preventable
"It's very important for travellers heading off to Europe to make sure they are up to date on their immunisations and that their children are too," she said.
Those who have already had measles or have been inoculated are not considered at risk of contracting the virus, the CDC said. The CDC recommends children receive two doses of measles, mumps and rubella vaccine starting at 12-15 months of age.
More than 90% of US children have been vaccinated against measles, the CDC said.
"We don't have to have this much measles," Dr Schuchat said. "Measles is preventable. Unvaccinated people put themselves and other people at risk for measles and its complications."
(David Beasley, Reuters Health, April 2012)
Many misconceptions about immunisation