Roughly a hundred people have been infected by a highly contagious norovirus in Maine, the CDC reports.

On Friday, the Maine Center for Disease Control and Prevention reported identifying 97 cases associated with a norovirus outbreak. The source seems to be the Woods Pond Beach, according to Bridgton Town Manager Bob Peabody, as all infectees either swam there or came into contact with someone who did.

These individuals reported experiencing symptoms such as vomiting, diarrhea, fever, and cramps over several days. The symptoms generally lasted a few days. Authorities in the town of Bridgeton closed down the beach on July 6th, following the first reported infections, to identify and deal with the source of the infections.

Norovirus causes gastrointestinal disease and can spread in a multitude of ways. You can contract the virus by eating contaminated food, touching an infected surface and then touching your mouth, or by having contact with someone who is infected. It’s especially virulent in areas where large numbers of people share limited space — such as hospitals, schools, or more famously, at the Winter Olympics in Korea. In the Maine outbreak, beachgoers 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 also 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,” Peabody told the Portland Press Herald. “I think the message is, if you’re sick or your children are sick, don’t go to the beach.”

Water samples taken on July 9th from the pond and the sinks in a public bathroom on the beach were tested for E. coli — the results showing that the swimming water contained safe levels of the bacteria. However, water from the taps was found to be above the safe limit. The sinks themselves were removed and hand sanitizers were installed as an extra precaution before the beach was re-opened for public access on July 10th.

Hot weather generally makes dipping spots much more prone to contamination, as a large number of people hit the beaches to cool off. A single carrier can infest the water (bacteria such as norovirus can be spread by infected individuals vomiting in the water, for example), and bacteria have a much easier time thriving in hot waters.

“We’re seeing the effects of climate change and temperature on lakes,” said Colin Holme, executive director of the Lakes Environmental Association, explained for the Portland Press Herald. “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.”

Authorities recommend that beachgoers wash their hands and practice good hygiene both before and after taking a dip. If you’re going to the beach with an infant, you should change their swim diapers frequently, preferably in a bathroom away from the water, and dispose of them in a trash container. Swimmers, in general, should also avoid swallowing water.

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