Initially, the illness appeared to spread only from animals to people. Then, experts said there was evidence of “limited” human-to-human transmission. Now, more cases are emerging among people with no known exposure to the animal markets, and in medical staff members caring for infected patients.
“Now that you have a cluster of 14 health care workers infected, it suggests that the potential for spread is much greater,” said Dr. Ian W. Lipkin, director of the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health in New York, who has researched SARS and MERS.
“I saw film footage of a hospital lobby in Wuhan, and they are wearing full personal protective equipment from head to toe,” he said. “They are taking it very seriously. I still don’t think this is as bad as SARS, but it’s worse than they originally portrayed it.”
Dr. Denison said that with both SARS and MERS, there were episodes in which individual patients became “super-spreaders” who infected many other people, for unknown reasons.
“That’s a wild card we don’t know, the capacity to have multiple transmissions from one person,” Dr. Denison said. “There was no evidence they had dramatically different virus.”
It is possible, he said, that super-spreaders had received a high dose of the virus and had more of it to transmit. Alternatively, their immune systems might have not been able to control the virus, allowing it to multiply and spread extensively in their bodies, making them more contagious.
Although no drugs have been approved specifically to treat coronavirus diseases, Dr. Denison said that in animal studies, an antiviral called remdesivir appeared effective. He has been working with other researchers to develop treatments.