May 18, 2015

Study Highlights Risk of Norovirus From Swimming

CDC offers tips to help swimmers stay safe in various swimming venues

norovirus centers for disease control and prevention healthy and safe swimming

When most people think of norovirus, they think of people marooned on a cruise ship with raging stomach and intestinal illness, unable to leave their cabins. However, an outbreak at an Oregon lake underscores that swimming also can put the public at risk of catching this disease. Fortunately, following a few easy and effective steps can help maximize the health benefits of swimming while minimizing the risk of getting sick.

In honor of Healthy and Safe Swimming Week, experts from the Centers for Disease Control and Prevention (CDC) and local and state health officials in Oregon reported on a summer 2014 outbreak that spread via swimming in a contaminated lake.

The norovirus outbreak in July 2014 linked to a lake near Portland, Ore., sickened 70 people. Those who swam in the lake were 2.3 times more likely to develop vomiting or diarrhea than those who visited the park but did not go in the water. More than half of those who got ill were children between four and 10 years old. Experts believe the outbreak began after a swimmer infected with norovirus had diarrhea or vomited in the water and other swimmers swallowed the contaminated water. To prevent other people from getting sick, park officials closed the lake to swimmers for 10 days.

“Children are prime targets for norovirus and other germs that can live in lakes and swimming pools because they’re so much more likely to get the water in their mouths,” said Michael Beach, Ph.D, associate director for healthy water for CDC. “Keeping germs out of the water in the first place is key to keeping everyone healthy and helping to keep the places we swim open all summer.”

A free downloadable brochure with tips about staying healthy and safe while enjoying pools and lakes this summer is available at CDC’s Healthy Swimming site.

Norovirus was the second-leading cause of outbreaks in untreated recreational water, such as lakes, from 1978 to 2010. It can live in water for several months or possibly even years. Swimming venues that are not treated with chlorine can pose a particular risk since there are no chemicals to kill the stomach virus.   

May 18 to 24, 2015, marks the 11th annual Healthy and Safe Swimming Week (formerly known as Recreational Water Illness and Injury Prevention Week). This observance highlights ways in which swimmers, parents, pool owners and operators, beach managers, and public health can maximize the health benefits of water-based physical activity, while minimizing the risk of recreational water-associated illness and injury.