(AP) -- U.K. health officials are increasing their surveillance for any potential disease outbreaks that could disrupt the London Olympics this summer.
An estimated 3 million visitors are expected to descend on the city during July and August, bringing with them viruses and bacteria from around the world.
At a meeting Tuesday of international disease experts, some said even though an outbreak was unlikely, officials couldn't take the risk of not being prepared for the Olympics, which are taking place from July 27 to Aug. 12.
"No news will be good news," said John McConnell, editor of the Lancet Infectious Diseases, which co-sponsored the meeting on health in mass gatherings.
He said large sports events like the Olympics typically have not had major outbreaks in the past.
But to get ready, British health authorities are boosting checks for infectious diseases and increasing labs' capacity to test samples. During the games, officials will get daily health reports on potential trouble spots and first-aid clinics will operate at event sites.
Britain's Health Protection Agency said it will mostly be looking for ailments like flu, diarrhea and respiratory illnesses but its surveillance system should be able to pick up rarer infections.
Scientists from Saudi Arabia shared their experiences from monitoring the Hajj, the world's largest annual mass gathering, which draws more than 2.5 million religious pilgrims to Mecca every year. Nearly 200,000 people come from developing countries, and the event helped spread polio outbreaks several years ago from Nigeria to Indonesia.
The U.S. Centers for Disease Control and Prevention advises Americans planning to travel to Britain to ensure they're up to date on their routine vaccinations, including measles. Europe has yearly outbreaks of the highly infectious disease.
Last month, the top doctor for Britain's Olympic team advised athletes not to shake hands to avoid catching any diseases.
McConnell dismissed that advice as "utterly unrealistic," noting infections were passed on just as easily by touching contaminated surfaces.
"You are just as likely to catch something by touching a dirty handrail ... so there's no reason not to shake hands," he said.
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