Men are the main COVID-19 transmitters: lessons from couples

Background: COVID-19 has affected millions of people worldwide. Clinical manifestations range from severe cases with a lethal outcome to mild or asymptomatic cases. Although there is the same proportion of infected genders, men are more susceptible to severe COVID-19, with a higher risk of death than women. This sex-bias may be explained by biological pathways. Methods: We performed an epidemiological survey from July 2020 to July 2021 including 1744 unvaccinated adult Brazilian couples with at least one infected spouse despite living together during the COVID-19 infection without protective measures. The presence or absence of infection was confirmed by RT-PCR and/or serology results. The couples were divided between groups where both partners were infected (concordant couples) or only one spouse remained asymptomatic despite the close contact with the infected one (discordant couples). Statistical analysis of the collected data was performed aiming to verify a differential transmitter potential between genders in household contact. Results: The combination of our data collected from concordant and discordant couples showed that the man is the first (or the only) affected in the major occurrences when compared to women. Our findings support other published surveys and are in concordance with previous studies of our group. Conclusions: These observations support the hypothesis according to which male individuals are more efficient virus transmitters than females, independently of the use of protective masks. In short, the present study confirmed the existence of gender differences not only for susceptibility to infection and resistance to COVID-19 but also in the transmission rate.