How Worried Should You Be About the Wuhan Coronavirus?

Some 2,800 people have been infected and 81 have been killed by the new coronavirus that began spreading from a seafood market where wild animals were sold for food in Wuhan, China. Public health officials have quarantined 50 million people in the region surrounding Wuhan and report that more than 30,000 people who have had close contact with infected persons are currently under close medical observation.

In the United States, the Centers for Disease Control and Prevention (CDC) has screened some 2,400 travelers arriving from Wuhan at five major airports. Of the 110 people that the agency is tracking and testing for infection, five have tested positive, 32 have tested negative, and results are still pending for 73 people.

Some evidence has emerged that infected people may be contagious before they show signs of infection. If so, this would make it more difficult for public health officials to prevent further spread of the disease by tracing, tracking, treating, and medically isolating people who may have come into contact with infected folks.

In trying to predict how the disease may spread, epidemiologists are trying to figure out what the basic reproduction number (R₀) is for the new coronavirus—that is, the number of people on average to whom an infected person will pass along the disease. For example, the R₀ for seasonal influenza is estimated to be around 1.3 people exposed to an infected person. According to CDC data, 35.5 million Americans suffered from flu last year and 34,200 died of it, yielding a mortality rate of around 0.1 percent.

A preliminary study by Chinese researchers suggest that the R₀ is around 3 for the Wuhan coronavirus, meaning it’s more contagious than seasonal influenza. That study also noted that by January 24, some 1,287 cases had been confirmed, resulting in 41 deaths. Those raw numbers yield an alarming mortality rate of over 3 percent. (For what it’s worth, the R₀ for the Black Death in medieval Europe was also around 3, but the mortality rate after disease onset was close to 100 percent.)

A preprint by British researchers analyzing the epidemic in Wuhan estimated that only about 5 percent of infections had been actually identified by January 24 which suggests that about 26,000 people were then suffering from the disease. If that estimate is correct, a rough calculation would yield a 0.15 percent mortality rate for the Wuhan virus. Parsing the latest reported cases and deaths yields essentially the same mortality rate. The coronavirus mortality rate is a bit above the seasonal flu rate in the U.S., but not hugely so.

Of course, these crude and provisional calculations do not warrant complacency. On the other hand, the speed with which Chinese scientists using modern biomedical technologies identified the virus and subsequently provided public health agencies and researchers around the world with the genetic information needed to track it is heartening. We will soon learn if humanity’s increasing biotechnical prowess combined with vigorous public health responses can prevent Wuhan’s coronavirus from developing into a modern pandemic.