Emerging data on the new virus circulating in China adds to evidence there is sustained human-to-human transmission in the city of Wuhan, and that a single case was able to ignite a chain of other infections.
The World Health Organization reported Thursday that there have been at least four generations of spread of the new virus, provisionally called 2019-nCoV, meaning a person who contracted the virus from a non-human source—presumably an animal—has infected a person, who infected another person, who then infected another person.
It’s not clear from a WHO statement whether transmission petered out after that point, or whether further generations of cases from those chains are still to come.
The WHO said the current estimate of the reproductive rate of the virus—the number of people, on average, that each infected person infects—is between 1.4 and 2.5. To stop an outbreak, the reproduction number has to be brought below one.
“That gives me no comfort at all that anything that’s happening right now is going to bring this under control any time soon,” Michael Osterholm, director of the University of Minnesota’s Center for Infectious Disease Research and Policy, said of the data the WHO released.
“And I think that as long as the virus is circulating in China as it appears to be, the rest of the world is going to be constantly pinged with it, as a result of people traveling to and from China in the near future,” he said.