At the start of the COVID-19 pandemic, the initial reports showed that SARS-CoV-2 infection promotes pneumonia in mainly older adults, which were the group with a major risk of getting hospitalized and getting mechanical ventilation due to severe COVID-19 disease (Berumen et al., 2020; Giannouchos et al., 2020; Zheng et al., 2020). However, other age-groups had similar risks due to different factors. Moreover, with regard to control of the pandemic, asymptomatic people have attracted attention due to their ability to transmit the virus without manifesting infection symptoms, which makes them identifiable only by difficult massive tests on the general population.
