Keep in mind that “the risk of infection is low in all countries with continued high coverage of polio vaccination and strong sanitation and safe water supplies,” said David Heymann, a professor of infectious disease epidemiology at London School of Hygiene and Tropical Medicine. For example, in the United Kingdom, which is on the advisory list, there have been no confirmed cases of paralysis caused by polio caught in the U.K. since 1984. But as long as polio continues to circulate in some parts of the world, Heymann said, “there is a risk to all countries.”