There is still no approved vaccine against COVID-19 and there are few pharmaceutical options for the treatment of COVID-19 in the USA.

Therefore, non-pharmaceutical interventions—such as the wearing of masks, social distancing, increased testing and the isolation of infected people—are the only tools available for reducing transmission.

Christopher Murray and colleagues present a state-level epidemiological analysis of the spread of SARS-CoV-2 infection across the USA and the impact of non-pharmaceutical interventions, from the first recorded case to 21 September 2020. Using a ‘Susceptible, Exposed, Infectious, Recovered’ framework, the authors include projections of several variables—including seasonal pneumonia, mobility, testing rates and mask use per capita—to assess various scenarios of social-distancing mandates and levels of mask use from 22 September 2020 to 28 February 2021.

Under all scenarios, the authors find that the USA is likely to face a continued COVID-19 public-health challenge through the winter, with populous states—such as California, Texas and Florida—in particular facing high levels of illness, deaths (as many as 511,373) and demands on hospital resources.

However, new epidemics and resurgences are not inevitable, the authors suggest. Several countries have sustained reductions in COVID-19 over time.

Mask use is a relatively affordable and low-impact intervention that can save lives across the USA.

The authors estimate that universal mask use (if 95% of the population in each state always wore a mask when in public) could save an additional 129,574 lives through the end of February 2021, or an additional 95,814 lives under a scenario of less adoption of mask wearing.