From the World Cup to Mecca: Can Big Events Spread Diseases?

Catching a disease may be the last thing on your mind as people gather for commencement ceremonies, sporting events or religious pilgrimages in the coming months, but they may be sharing more than memories when they come together.

Gatherings that draw people from all over the world will occur in places with diseases such as MERS, dengue fever, measles and mumps, but experts say the risks are quite low.

"We acknowledge that we live in a tight little world with people traveling," said Dr. William Schaffner, who chairs preventive medicine at Vanderbilt University in Nashville, Tennessee. "Think about how many graduation events take place every spring, all kinds of congregations that occur. We don't see outbreaks of communicable diseases following those because we are generally a well-protected population. In addition, we have a very knowledgeable and responsive public health system."

Pilgrimage to Mecca

Saudi Arabian officials have already raised the alarm on the country's potential to spread the MERS virus during Islam's annual Hajj pilgrimage to Mecca in the fall.

Health officials have been concerned about meningitis spreading in pilgrimages past, which has led to special precautions, Schaffner said. Though MERS, or Middle Eastern Respiratory Syndrome, has no known cure, Schaffner said teams are on hand and prepared to handle potential infections.

Click here to find out how you can protect yourself from MERS.

MERS is fatal to one in three people who contract it, but it doesn't spread as readily as its cousin, the SARS virus, which infected 8,098 people from November 2002 through July 2003, and killed 774 of them. However, health care workers and those in close contact with MERS patients have been more susceptible to it, according to the World Health Organization.

Since April 2012, WHO has reported 536 laboratory confirmed cases of MERS in more than a dozen countries. But between late March and early May, Saudi Arabia has reported 290 new cases.

Two cases were reported in the United States this month in people who had recently traveled to Saudi Arabia, but the virus seems not to have spread.

Read more about the U.S. MERS cases here.

World Cup

Everyone seems to have soccer fever during the World Cup, but researchers in Spain, Brazil and the United Kingdom suspect there's a chance spectators traveling to some Brazilian cities this June and July could also catch dengue fever.

People are infected by mosquitoes then travel back home, "and then local mosquitoes can pick it up," Schaffner said. "It happens remarkably infrequently, but that is how dengue has been imported into south Florida from the Caribbean."

Dengue fever, which is transmitted through mosquito bites, is one of the leading causes of illness and death in the tropics, according to the Centers for Disease Control and Prevention. Its symptoms can include difficulty breathing, bloody gums and vomiting blood.

It may take three weeks to transmit the virus from a sick human to a mosquito to another human, but researchers wondered whether the climate forecast coupled with the influx of more than a million soccer fans to Brazil could foster the spread of infection, according to their study published Friday in the British medical journal The Lancet.

The researchers set out to identify Brazilian cities that needed to control their mosquito population in advance of the tournament. They identified three cities at higher risk for having epidemic dengue fever at the start of the games in June.

Graduation Ceremonies

Measles, mumps and other contagious diseases have surged this year, but Schaffner said the viruses shouldn't mar any graduation ceremonies. The gatherings bring large groups of people together -- sometimes in places where there's been an outbreak -- but he said graduation weekends are too short to really worry about disease spread.

Read about how measles and mumps are making a comeback in Ohio.

He said people can take comfort in the knowledge that most people in the United states are immune from the measles and the mumps because they've been vaccinated, and there haven't been many graduation- or concert-related outbreaks.

"When we slip up, we let infectious diseases come in the side door," Schaffner said. "The classical current example is parents withholding their children from vaccinations, going abroad, picking up measles and bringing it back to spread it to other children. ... That's a chink, a crack in our protective armor."