Data Analysis Suggests that Social Distancing Works

Stock image with blue background and up close view of COVID-19 (coronavirus) molecules.
Public Health Prof. David Kriebel says that the data from the first 25,000 cases of coronavirus cases in Wuhan show that the reproductive number dropped from 3 people to .03, which means that social distancing and isolation is working to contain the spread of COVID-19.

By Karen Angelo

Epidemiologist and Public Health Prof. David Kriebel, who is reviewing data as it becomes available on the outbreak of COVID-19, sees cautiously encouraging trends on the containment of the virus emerging in China. 

A preliminary report (not yet peer-reviewed) by epidemiologists in Wuhan and at Harvard that analyzed the first 25,000 cases in Wuhan found that before social isolation, each person infected with the disease passed it to about three people on average every five days. This increased the number of cases exponentially. As China enacted aggressive quarantine and social isolation measures, the tide turned, according to the report. 

“The good news in Wuhan is that by mid-February, the basic reproductive number fell from three to 0.3 after officials quarantined infected cases, traced their contacts and instituted strong social distancing measures,” says Kriebel, who directs the Lowell Center for Sustainable Production and is based in the Zuckerberg College of Health Sciences. “When this number is less than one, it means that the epidemic is dying out and that new cases don’t reproduce themselves.”

If the model is correct and conditions continue as they were in late February, the data suggest that there will be no new cases in Wuhan, a population of 10 million, by the end of April or early May. 

While scientists don’t know where the U.S. is along the curve of growth of the infection, they now have encouraging evidence that social distancing slows down the rapid spread of the coronavirus. 

“We must do everything we can to stop the spread by avoiding large groups and keeping our distance from each other,” says Kriebel. “The decisions made by state and local governments this past week to close schools and limit social gatherings are among the most important tools we’ve got to control the spread of the disease.” 

He stresses that from all indications, COVID-19 is both more easily spread and dangerous than the seasonal flu. 

“COVID-19 is more lethal than the flu and will severely tax the health care system,” Kriebel says. “In addition, if hospitals fill up with COVID-19 cases, they will not be able to care for people who are sick for other reasons.” 

What are the Possible Outcomes? 

Kriebel says that the data from Wuhan suggests that a majority of people who become infected will experience only mild symptoms or be asymptomatic. They will most likely become immune from the disease after their infection. Unfortunately, during their infection, they may be able to infect others, which is one of the main reasons that social distancing, and not just isolating only sick people, is so important. 

“Think of it this way: by isolating yourself, you are protecting yourself from getting sick and also participating in a collective action to drive down the spread of the disease, which will protect many others whom you do not know – but who should thank you for helping them stay healthy,” Kriebel says.