Editor’s Note: This story was updated on Mar. 16 to reflect the President’s Coronavirus Guidelines for America and orders by Bay Area counties to shelter in place.

As cities and towns across the United States confront the growing number of COVID-19 cases, epidemiologists say we are now in the mitigation phase of the outbreak. The virus is already in our communities, so the focus now is to mitigate, or reduce, the damage from the disease.

The news is full of reports about cities canceling events and closing schools as well as businesses urging employees to work from home if possible.

UC San Francisco epidemiologists Jeff Martin, MD, MPH, and George Rutherford, III, MD, explained why these public health measures are being taken and what each of us can do to slow the outbreak and help to save lives.

Above all, keep your distance.

“‘Social distancing’ will be the key phrase in the days and weeks to come,” said Martin. The term simply refers to avoiding close contact with other individuals in order to avoid catching the virus yourself and to avoid passing it on.

Social distancing is currently the most important factor we can control in the COVID-19 outbreak, and therefore critical, explained Martin. Many factors contribute to the so-called reproductive number of the new coronavirus, which describes roughly how many people an infected individual will go on to infect. Currently, estimates of the reproductive number of the novel coronavirus range from 1.4 to 6.5, with an average of 3.3.

“The higher the reproductive number, the faster it will spread,” said Martin. Factors that affect the reproductive number include how inherently contagious the virus is, how susceptible people are to infection, the number of contacts between people, and the duration of those contacts.

“We’re not at a stage to modify the first two factors – the biologic behavior of the virus or the susceptibility of individuals – but each of us can decrease the number and duration of our contacts with others,” said Martin.

Social distancing can also effectively extend to environmental precautions such as disinfecting often-touched surfaces that may pass on the virus, said Martin. He offered a phrase borrowed from camping, “leave no trace behind,” when practicing these precautions.

What social distancing means in daily life.

Many cities have encouraged social distancing by banning large gatherings, encouraging telecommuting and closing schools. Rutherford advised avoiding crowded public transportation if possible. Social activities are now discouraged, but what does social distancing mean for essential activities? Those decisions may depend on your age and susceptibility to infection. “If you’re over 60, you should be laying low, staying home,” said Rutherford.

For younger people, Martin pointed out that anyone who becomes infected can spread the virus to an older person or someone who is immunocompromised. “So, the fewer young persons who become infected, the lower the incidence in the older population,” he said.

According to the President’s Coronavirus Guidelines for America, everyone should avoid social gatherings of more than 10 people, and avoid eating or drinking at bars, restaurants, and food courts. If someone in your household has tested positive for the coronavirus, keep the entire household at home.

In the Bay Area, a number of counties including San Francisco have issued orders to shelter in place from March 17, 2020, through April 7, 2020. Everyone should stay at home except for certain essential activities, such as grocery shopping or to seek medical care, or to perform work for essential businesses, government agencies, or public infrastructure construction.

Nina Bai

Posts by Nina Bai