Pitt expert, others warn coronavirus remains lethal despite falling numbers

Suggesting the coronavirus is less lethal now than it was two months ago — as a UPMC doctor appeared to do on Thursday — would be a mistake, other experts warned.

Although the prevalence and severity of covid-19, the respiratory illness caused by the coronavirus, has declined across the region, experts said little has changed about the virus that has infected close to 7 million people worldwide and killed nearly 400,000.

Doctors at hospitals in Northern Italy and at UPMC facilities in Western Pennsylvania and elsewhere say they are seeing a lower ratio of positive covid-19 tests and less lethal cases of the illness. But the announcements may have as much to do with earlier testing and treatment as well as efforts to mitigate the spread of the disease, including the three-month pandemic shutdown and the widespread adoption of face masks and social distancing.

Although viruses do mutate and change with time, Vaughn Cooper, a University of Pittsburgh professor who holds a doctorate in microbiology and molecular genetics, said that does not appear to be the case with the coronavirus.

“In fact, there is no evidence that the virus has evolved in functionally significant ways that would influence disease severity. It’s just as dangerous as ever,” said Cooper, who heads the Center for Evolutionary Biology and Medicine at Pitt’s medical school.

Cooper, who has studied the evolution of infectious diseases for 20 years, said he fears the announcement out of UPMC that the severity and prevalence of the virus are declining could create the dangerous impression that it is no longer lethal.

A UPMC spokesman did not immediately respond to a request for comment.

Cooper said a number of factors could account for the region’s low prevalence of covid-19. Originally, tests were offered only to those who already had symptoms. Now, they are broadly available, including for people with no symptoms. An earlier diagnosis, coupled with earlier treatment and isolation, also could be factors.

“And we are a less-densely populated community, we have less public transit. Maybe the people who traveled abroad and brought it back had fewer social contacts and maybe they just did a better job of self quarantining. This is something we’re following up on,” Cooper said.

Unlike the flu, which returns in new variants every year, coronaviruses tend to mutate slowly, he said.

In agreement is Dr. Amesh Adalja, a Pittsburgh-based fellow of the Infectious Disease Society of America. While numbers UPMC doctors and those in Italy cite are encouraging, Adalja said there is no evidence the virus itself has changed. So scientists need to determine what happened.

“Is the viral load lower now than in March? If we’re diagnosing them earlier, we may be catching it before the viral load is at its peak. It is not any difference in the virus, just that we’re testing earlier. One other theory is we’re doing so much social distancing that people are getting infected at lower loads. I think it is important to look for that,” he said.

Dr. Michael Ryan, an epidemiologist and infectious disease specialist with the World Health Organization, offered similar cautions this week, following news out of Northern Italy, where a doctor announced viral levels were so low the virus is no longer a threat.

“This is still a killer virus, and there are still thousands of people everyday dying from this virus,” Ryan said. “So, we need to be exceptionally careful not to create a sense that, all of a sudden, the virus by its own volition has now decided to be less pathogenic. That is not the case at all.”

He noted the virus is still raging in South America and Africa, even as it appears to be waning in Europe and North America.

And there are fears recent mass protests could trigger new hot spots across the United States in coming weeks.

Over the last three months, scientists have gained an evolving understanding of the virus believed to have originated in China late last year. They now know that only about 20% of those who contract covid-19 tend to spread the contagion.