In a new study, researchers found if physical distancing measures in the United States are relaxed while there is still no COVID-19 vaccine or treatment and while personal protective equipment remains in short supply, the number of resulting infections could be about the same as if distancing had never been implemented to begin with.
The research was conducted by a UCLA-led team of mathematicians and scientists.
The researchers compared the results of three related mathematical models of disease transmission that they used to analyze data emerging from local and national governments, including one that measures the dynamic reproduction number—the average number of susceptible people infected by one previously infected person.
The models all highlight the dangers of relaxing public health measures too soon.
The team found distancing efforts that appear to have succeeded in the short term may have little impact on the total number of infections expected over the course of the pandemic.
The mathematical models demonstrate that relaxing these measures in the absence of pharmaceutical interventions may allow the pandemic to reemerge.
The findings are applicable to both future spikes of COVID-19 and future pandemics.
The team says if distancing and shelter-in-place measures had not been taken in March and April, it is very likely the number of people infected in California, New York, and elsewhere would have been dramatically higher, posing a severe burden on hospitals.
But the total number of infections predicted if these precautions end too soon is similar to the number that would be expected over the course of the pandemic without such measures.
In other words, short-term distancing can slow the spread of the disease but may not result in fewer people becoming infected.
Mathematically modeling and forecasting the spread of COVID-19 are critical for effective public health policy, but wide differences in precautionary approaches across the country have made it a challenge.
Social distancing and wearing face masks reduce the spread of COVID-19, but people in many states are not following distancing guidelines and are not wearing masks—and the number of infections continues to rise.
The team says this study predicts a surge in cases in California after distancing measures are relaxed.
Alternative strategies exist that would allow the economy to ramp up without substantial new infections. Those strategies all involve significant use of face masks and increased testing.
One author of the study is Andrea Bertozzi, a distinguished professor of mathematics.
The study is published in PNAS.
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