Summer means party time and backyard barbecues, but they may also be the hotbed for COVID-19 infection. Experts say that informal parties, gatherings with family and friends, are creating outbreaks of coronavirus clusters.

While restaurants and bars have been shuttered in many states to try and stop the transmission of disease, health officials warn that even private gatherings with people you know can become highly contagious venues for spreading the coronavirus. They cite cases particularly in Florida, Michigan, Oregon and New Jersey where private parties caused clusters of COVID-19 cases.

Expert said that all to frequently, people are lulled into a” false sense of security” because they know most of the guests in attendance.

According to Today, dozens of lifeguards in New Jersey and 20 teenagers in the same state tested positive for the virus after attending house parties. At least 13 people tested positive after a party in Cape Cod, Massachusetts that was attended primarily by restaurant workers. This forced many local eateries to close, according to The Boston Globe.

Mike DeWine, the governor of Ohio, said he was worried about how these informal get-togethers are spreading the virus. “I think there’s a general tendency when we’re with people we know maybe not to be as concerned,” he said, according to Today.

Ohio resident Jill Parker said she attended a family gathering on the Fourth of July where all but 3 of the 14 people in attendance tested positive for the coronavirus.

“We got too comfortable,” she told Today. “We had a false sense of security, and as the evening progressed, and we’re swimming and we’re outside and having fun, it just seemed unlikely there was any danger that we really dropped our guard.”

According to news reports in Ohio, most of the people who attended these super spreading house parties didn’t wear masks — even if they were offered.

“The virus is real,” DeWine said. “We certainly can’t let our guard down.”

For tips on throwing a safe social gatherings during the pandemic, click here.