To mask or not to mask: Modeling the potential for face mask use by the general public to curtail the COVID-19 pandemic

Steffen E. Eikenberry; Marina Mancuso; Enahoro Iboi; Tin Phan; Keenan Eikenberry; Yang Kuang; Eric Kostelich; Abba B. Gumel

Considering a fixed transmission rate, β 0 , 80% adoption of 20%, 50%, and 80% effective masks reduces cumulative relative (absolute) mortality by 1.8% (4,419), 17% (41, 317) , and 55% (134,920), respectively, in New York state. In Washington state, relative (absolute) mortality reductions are dramatic, amounting to 65% (22, 262) , 91% (31, 157) , and 95% (32,529). When β(t) varies with time, New York deaths reductions are 9% (21,315), 45% (103,860), and 74% (172,460), while figures for Washington are 24% (410), 41% (684), and 48% (799). In the latter case, the epidemic peaks soon even without masks. Thus, a range of outcomes are possible, but both the absolute and relative benefit to weak masks can be quite large; when the relative benefit is small, the absolute benefit in terms of lives is still highly nontrivial. Most of our model projected mortality numbers for New York and Washington state are quite high (except for variable β(t) in Washington), and likely represent worst-case scenarios as they primarily reflect β values early in time. Thus, they may be dramatic overestimates, depending upon these states' populations ongoing responses to the COVID-19 epidemics. Nevertheless, the estimated transmission values for the two states, under fixed and variable β(t) represent a broad range of possible transmission dynamics, are within the range estimated in prior studies [43, 44, 38] , and so we may have some confidence in our general conclusions on the possible range of benefits to masks. Note also that we have restricted our parameter estimation only to initial conditions and transmission parameters, owing to identifiability problems with more complex models and larger parameter groups (see e.g. [46] ). For example, the same death data may be consistent with either a large β 0 and low δ (death rate), or visa versa.