Forecast predictions for the COVID-19 pandemic in Brazil by statistical modeling using the Weibull distribution for daily new cases and deaths

Abstract COVID-19 has killed more than 330.000 people worldwide and more than 21,000 Brazilians. Since there are no specific drugs or vaccines, the available tools against COVID-19 are preventive, such as the use of personal protective equipment, social distancing, lockdowns and mass testing. Such measures are hindered in Brazil due to a restrict budget, low educational level of the population and misleading attitudes from the federal authorities. Predictions for COVID-19 are of pivotal importance to subsidize and mobilize health authorities’ efforts in applying the necessary preventive strategies. The Weibull distribution was used to model the forecast prediction of COVID-19, in four scenarios, based on the curve of daily new deaths as a function of time. The date in which the number of daily new deaths will fall below the rate of 3 deaths per million, the mean level considered by some countries to relax stay-at-home measures, was estimated. If the daily new deaths curve was bended today (i. e. about 1,250 deaths per day), the predicted date would be on June 18th. Analysis of the lethality rate allowed the estimation of daily new cases and total death toll at the end of the outbreak. Our results suggest that each additional day that lasts to bend the daily new deaths curve can correspond to additional 3,718 deaths at the end of COVID-19 outbreak in Brazil (R2 = 0.9938). Predictions of the outbreak can be used to guide Brazilian health authorities in the decision making to properly fight COVID-19 pandemic.