Over half of people infected with COVID-19 don’t know how they caught it, CDC says

More than half of COVID-19 patients don’t know how they got infected, according to a new report from the Centers for Disease Control and Prevention.

In a survey of coronavirus inpatients and outpatients across different states, 54% couldn’t pinpoint their source of infection. The remaining 46% said they had recent contact with someone they knew or later learned was infected, typically family members and coworkers, the CDC report states.

“It’s very concerning,” Dr. Joshua Barocas, an infectious disease physician at Boston Medical Center, said of the findings during a briefing by the Infectious Diseases Society of America.

The fact that so many patients can’t point to an infected person who may have been exposed them to the virus underscores a big reason it spreads so easily, Barocas said, many people show no symptoms.

“We’ve seen that asymptomatic disease is incredibly common,” he said, and it occurs among both low- and high-risk populations.

This makes contact tracing efforts much more difficult, Barocas added. There’s no way to follow an infection back to its source if the victim can’t reliably narrow down a time, a place, or even a person to investigate.

Ricardo Franco, an associate scientist at the Center for AIDS Research, shared Barocas’ concerns.

The report — which surveyed about 350 adult patients — serves as a reminder of the many different ways the disease can sneak into the human body, Franco said.

The culprit isn’t always a family member, a friend or a colleague at work. It’s often that “anonymous door handle, or gas pump handle, or that indoor environment carrying some droplets … that can’t point to any single person,” Franco said.

Health officials, including the nation’s top infectious disease expert Dr. Anthony Fauci, have continually emphasized the importance of contact tracing for monitoring and controlling outbreaks. But during a CNN interview last week, he said “I don’t think we’re doing very well.”

Part of the problem is there aren’t enough tracers, and most of those tracers are trying to track infection by phone — which Fauci believes won’t work, they need to be on the ground and in the communities.

Still, Fauci acknowledges the new disease defies much of what the standard pandemic playbook recommends.

The CDC report makes the reason clear.

“When you have community spread, it’s insidious because there are so many people in the community who are infected but asymptomatic,” he said. “So the standard classic paradigm of identification, isolation, contact tracing doesn’t work no matter how good you are because you don’t know who you’re tracing.”

This story was originally published July 3, 2020 at 5:43 PM.