U.S. health officials are urging Americans traveling to London for the summer Olympics to make sure they are up-to-date with measles immunizations, warning that unvaccinated tourists could become infected and spark an outbreak at home.
"Disease knows no borders," said Rebecca Martin, director of the CDC's Global Immunization Division. "We are concerned about Americans coming back from the Olympics this summer and unknowingly infecting others."
The London Olympics open on July 27 and the Euro 2012 soccer cup begins on June 8.
Health experts explain that huge public events, like the Olympics, increase the likelihood of infection among unvaccinated people and affected individuals might unknowingly carry the disease home.
According to the Indiana State Health Department, during last month's Super Bowl two people who were infected with measles attended a crowded event in downtown Indianapolis and touched off an outbreak that infected 16 people, The Wall Street Journal reported Tuesday.
Heath officials also say that most cases of the measles in the US are imported by travelers who have not been vaccinated.
A measles outbreak in San Diego in 2008 was traced to an unvaccinated seven-year-old boy who contracted the disease in Switzerland. He passed the disease on to 11 other unvaccinated children, The Journal reported.
More parents in the US are getting their children vaccinated than in recent years, when concerns about vaccinations prompted some parents to opt out, the Journal reported. According to the CDC, the rate of vaccination for measles, mumps and rubella was at 91.5 percent in 2010, up from 90 percent a year earlier.
Health experts say a community needs about a 95 percent immunization rate against measles to ensure "herd" immunity, according to The Journal.
Before routine vaccinations in the United States, the virus killed between 3,000 and 5,000 people each year.