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SAN DIEGO — A new report from Scripps Research finds that up to half of all people infected with COVID-19 show no symptoms, and many of them could have lung damage without realizing it.

The Scripps Research report was trying to understand how people without symptoms can spread coronavirus, but researchers made a startling discovery.

“Three studies that I’ve looked at studied asymptomatic people. Interestingly, all the people look and feel fine, but when researchers did a CT scan doing an image of their lungs, in 50 to 100% of the cases, they actually found abnormalities,” said Daniel Oran, of Scripps Research. “When they look at these CT scans, it’s hazy — looks like you’re looking through a dirty piece of glass. What that means is there’s something abnormal about the lungs.”

Oran, one of the authors of the report, analyzed data of coronavirus patients from around the world. They found that 40 to 50% of people who test positive for the virus are asymptomatic.

“We know that about half of all infections are spread before people have symptoms, so it’s important to know that distinction. The truth is, whether you’re asymptomatic or presymptomatic, when you look and feel fine you still can make others sick,” Oran said.

As businesses from bars and restaurants to amusement parks begin reopening, many people are letting down their guard. But Oran said that is a mistake. Gov. Gavin Newsom had the same message when he addressed residents Monday.

“This disease is six months old at the most, and we know so little about it and so few of us have any immunity,” Newsom said. “At this point in California, maybe 2 or 3% at most have been exposed to coronavirus. That means 97% of us have no immunity.”

The best way to protect yourself remains social distance and face coverings, experts say. Oran would even recommend investing in an N95 mask, but he said he is frustrated about the lack of supply.  

“Three or four months later, in our country we still do not have enough masks,” Oran said.

And for those who say they are not worried about contracting the coronavirus or don’t fit the profile of people at risk, Oran offered this example:

“There was a case last week, a young woman in Chicago in her 20s, good health, who contracted the coronavirus in April. Unfortunately, last week she required a double lung transplant. The surgeons said they had never seen lungs that had been so damaged,” Oran said. “So this is still a very very new disease we don’t know much about it.”