Three-quarters attack rate of SARS-CoV-2 in the Brazilian Amazon during a largely unmitigated epidemic.
Buss LF., Prete CA., Abrahim CMM., Mendrone A., Salomon T., de Almeida-Neto C., França RFO., Belotti MC., Carvalho MPSS., Costa AG., Crispim MAE., Ferreira SC., Fraiji NA., Gurzenda S., Whittaker C., Kamaura LT., Takecian PL., da Silva Peixoto P., Oikawa MK., Nishiya AS., Rocha V., Salles NA., de Souza Santos AA., da Silva MA., Custer B., Parag KV., Barral-Netto M., Kraemer MUG., Pereira RHM., Pybus OG., Busch MP., Castro MC., Dye C., Nascimento VH., Faria NR., Sabino EC.
SARS-CoV-2 spread rapidly in the Brazilian Amazon and the attack rate there is an estimate of the final size of a largely unmitigated epidemic. We use a convenience sample of blood donors to show that by June, one month after the epidemic peak in Manaus, capital of Amazonas state, 44% of the population had detectable IgG antibodies. Correcting for cases without a detectable antibody response and antibody waning, we estimate a 66% attack rate in June, rising to 76% in October. This is higher than in São Paulo, in southeastern Brazil, where the estimated attack rate in October is 29%. These results confirm that, when poorly controlled, COVID-19 can infect a high fraction of the population causing high mortality.