This is part of our Coronavirus Update series in which Harvard specialists in epidemiology, infectious disease, economics, politics, and other disciplines offer insights into what the latest developments in the COVID-19 outbreak may bring.
The number of confirmed cases of the coronavirus that originated in Wuhan surged to nearly 17,400 by Monday, and a Harvard epidemiologist says that it’s likely as many as 100,000 are already infected, so he expects the official tally to continue to climb steeply.
“Many epidemiologists and people who are following this outbreak closely are assuming that it’s probably quite a bit more widespread than the case counts suggest,” said Michael Mina, assistant professor of epidemiology at the Harvard T.H. Chan School of Public Health. “Many people also think that there’s probably over 100,000 in reality out in mainland China, for example. We just don’t capture all of those through the case reporting we have. … We can assume that this is growing at somewhat of an exponential rate, and it will continue increasing in scale.”
Mina, who participated in a Facebook Live event sponsored by The Forum at Harvard T.H. Chan School of Public Health and PRI’s “The World,” discussed what’s known and unknown about the virus with The World reporter Elana Gordon. The 30-minute session drew an online audience of about 13,000.
The virus originated in Wuhan, the largest city in central China, with a population of more than 11 million, and it spread rapidly there. More than 360 have died from the illness globally, nearly all of them in China, as are the vast majority of reported cases thus far, according to the World Health Organization’s Feb. 3 situation report. By comparison, 349 died in mainland China during the severe acute respiratory syndrome (SARS) outbreak in 2002 and 2003.
The new coronavirus has been found in 23 countries, and international health authorities last week declared it a public health emergency of international concern. The first death outside China was reported Sunday, in the Philippines. Inside the U.S., 11 cases have been confirmed in six states. China’s national health commission, meanwhile, said 189,583 people have been identified as having had close contact with infected patients.
Mina said knowledge is advancing rapidly, but the uncertainties around the new virus make it difficult to know even basic information, such as its death rate. The number of confirmed cases and deaths indicate that it is around 2 percent, significantly lower than SARS’ 10 percent. But if the case number is far larger, as is expected, it’s likely that the condition is fatal in far fewer cases than even the 2 percent, although the overall toll may be much higher.
Those and additional uncertainties — such as government responses, their effectiveness, and self-protective steps individuals may take — make predicting the epidemic’s path difficult, Mina said. Quarantines can slow transmission but also have negative consequences such as limiting resources needed to respond to illness within the quarantine area.
What’s known at this point, Mina said, is that it is a respiratory virus and so transmission is largely through droplets coughed or sneezed into the air. It is likely, he said, that the virus can survive for some time on surfaces like door knobs and tabletops, though transmission through that route is probably uncommon.