Americans headed into Labor Day weekend - the unofficial end to the Lost Summer of 2020 - amid warnings from public health experts that backyard parties, crowded bars and other gatherings could cause the coronavirus to come surging back.

"I look upon the Labor Day weekend really as a critical point," said Dr. Anthony Fauci, the government's top infectious-disease expert. "Are we going to go in the right direction and continue the momentum downward, or are we going to have to step back a bit as we start another surge?"

The rise in infections, deaths and hospitalizations over the summer, primarily in the South and West, was blamed in part on Americans behaving heedlessly over Memorial Day and July Fourth.

The landscape has improved in recent weeks, with the numbers headed in the right direction in hard-hit states like Florida, Arizona and Texas, but there are certain risk factors that could combine with Labor Day: Children are going back to school, university campuses are seeing soaring case counts, college football is starting, more businesses are open, and flu season is around the corner.

And a few states are heading into the holiday with less room in hospitals than they had over Memorial Day and the Fourth of July. Alabama, for example, had about 800 people hospitalized with the virus on July 1. This week, it has just under 1,000.

More beaches will be open on Labor Day than on Memorial Day, but Fauci said that is not cause in itself for concern, as long as people keep their distance.

"I would rather see someone on a beach, being physically separated enough, than someone crowded in an indoor bar," he said.

The outbreak is blamed for about 187,000 deaths and almost 6.2 million confirmed infections in the U.S., by far the highest totals in the world. Cases of COVID-19, which spiked from about 20,000 per day to around 70,000 during the summertime surge in the South, are now down to about 40,000.

Dr. Albert Ko, a Yale University epidemiologist, said he is concerned about students heading back to school across the nation next week after coming back from holiday travel and a weekend of social gatherings.

"Any transmission events that happen here could be amplified unless we're careful about it," Ko said. "Whether it's going to be a perfect storm, l don't think so. People are aware of the risk, and people have been socially distancing. But this is certainly a concern."

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