Tourists returning to the US from the London Olympics could become a cause for spread of measles epidemic in the country, the United States Centers for Disease Control has warned.
The CDC has asked Americans planning to visit London for the summer games to get vaccinated, and claimed that measles was common in Europe, and that "diseases know no borders".
Travellers to Ukraine and Poland for the Euro2012 football tournament in June could also put the US at risk of a measles outbreak, The Telegraph reports.
"Disease knows no borders. Ukraine is experiencing a large measles outbreak right now. We are concerned about Americans coming back from the Olympics this summer and unknowingly infecting others," said Rebecca Martin, director of the CDC's Global Immunization Division.
There were eight deaths and 26,000 cases of measles across Europe last year, including 1,086 in England and Wales.
That compares to an annual tally of 214 measles cases in the US in 2011, including three infants too young to be vaccinated who caught the disease in a California doctor's waiting room from a seven-year-old who had visited Switzerland.
Experts said that in recent years America had typically experienced only 50 cases a year, and blamed visitors to Europe for the increase.