Christy Dow of Naples sunbathes on July 7 at Woods Pond Beach in Bridgton, where a number of people reported falling ill after being in the water.

State scientists say norovirus is what made nearly 100 people sick this month after they swam at Woods Pond Beach in Bridgton or had contact with someone who did.

The Maine Center for Disease Control and Prevention released the findings of its investigation on Friday afternoon, two weeks after the town closed the beach following reports from people complaining of symptoms that included vomiting, diarrhea, fever and cramps. Norovirus is a gastrointestinal disease that spreads easily from person to person. People who put their heads under water or swallowed water while swimming were at greater risk of infection, but several people who were not at the beach caught got sick after caring for someone who was ill.

“It’s highly contagious, so it would appear that there’s a human element there, that somebody had it and was at the beach,” Bridgton Town Manager Bob Peabody said. “I think the message is, if you’re sick or your children are sick, don’t go to the beach.”

The town closed Woods Pond Beach on July 6. Multiple people had contacted the Maine CDC, saying they got sick after swimming at the beach earlier that week. Water from the pond and the sinks in the public bathroom was tested July 9. The beach reopened July 10 when the results showed the water from the swim area had E. coli levels within acceptable limits. The water from the bathroom taps failed, however, and the town planned to remove those sinks.

Peabody said the investigation identified 97 people who reported being ill and were associated with this outbreak. The symptoms generally lasted a few days. In addition to interviewing people who got sick, the Maine CDC tested two stool samples, according to its report to the town.

Norovirus is often associated with cruise ships, but it has been associated with lakes before. People can be infected by another person, contaminated food or water or by touching a contaminated surface. In 2015, the U.S. Centers for Disease Control and Prevention published a review of a similar outbreak that sickened 70 people in Oregon. In that case, experts believed a swimmer infected with norovirus had diarrhea or vomited in the water. Park officials closed the lake to swimmers for 10 days to prevent more people from getting sick.

“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,” Dr. Michael Beach, the U.S. CDC’s associate director for healthy water, said at the time. “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.”

Another town beach closed this week due to water contamination.

The Lewiston Sun Journal reported swimmers at the Otisfield town beach on Pleasant Lake had also gotten sick, and initial tests showed high levels of E. coli in the water. The beach was reopened Friday after tests showed the water is safe, according to an alert posted on the town website. A town official did not respond to requests for comment Friday.

The state does not track beaches that are closed due to contamination. Water testing typically takes place after people get sick, but town and state officials said there is no requirement to do it on a routine basis. The Maine Healthy Beaches Program, a collaboration between the state Department of Environmental Protection and the University of Maine’s Cooperative Extension, monitors most coastal beaches and posts daily updates about contaminants. There is no equivalent for freshwater beaches.

“Generally that ends up in the municipalities, because they’re really the front line,” said Linda Bacon, a lake biologist with the Maine DEP.

The Maine CDC was not consulted or informed of the outbreak in Otisfield, spokeswoman Emily Spencer said.

“The town is to be commended for testing the water and closing the beach to swimming while the risk of illness remains,” Spencer wrote in an email.

Experts said hot temperatures this summer have made lakes vulnerable to contamination. The number of people at local beaches surges, and the bacteria they bring with them thrives in warmer temperatures. And these cases could become more common.

“We’re seeing the effects of climate change and temperature on lakes,” said Colin Holme, executive director of the Lakes Environmental Association. “These problems could be more frequent in the future because the temperature is going to rise and people are going to seek the water in relief.”

To prevent the spread of illness, visitors at beaches are advised to wash their hands and practice good hygiene. Swim diapers should be changed frequently, preferably in a bathroom away from the water’s edge, and disposed properly in a trash container. Swimmers should avoid swallowing the water. People who are sick should say home.

“The more people you have, generally the higher bacteria concentrations you have,” Holme said. “It’s a problem that comes with us.”

Megan Doyle can be contacted at 791-6327 or at:

mdoyle@pressherald.com

Twitter: megan_e_doyle