Asymptomatic versus symptomatic SARS-CoV-2 infection: a cross-sectional seroprevalence study.

Background: Although symptomatic SARS-CoV-2 infection predisposes patients to develop complications, the asymptomatic SARS-CoV-2 infection state is of public health importance being a hidden source of infection. Moreover, the asymptomatic state may camouflage the actual burden of the disease.

Methods: Data of 1434 seropositive participants for SARS-CoV-2 spike (anti-S) and/or nucleocapsid antibodies (anti-N) were retrieved from a larger cross-sectional survey on COVID-19. Relevant data were retrieved from records including socio-demographic, medical, and behavioral characteristics of seropositive participants as well as history of COVID-19 symptoms during the last 6 months. Symptomatic/asymptomatic SARS-CoV-2 infection was categorized based on the history of the presence or absence of COVID-19 symptoms.

Results: The rate of asymptomatic SARS-CoV-2 infection was 34.9%. There was a statistically significant difference between symptomatic and asymptomatic participants regarding age, residence, medical conditions, habits, and infection control measures. The number of symptoms was positively correlated with anti-S titer and both were positively correlated with adult body mass index. Slum areas residence, client-facing occupation or being a healthcare worker, having lung disease, having blood group type A, never practicing exercise or social distancing, never using soap for hand washing, and minimal engagement in online working/studying were independent factors associated with the symptomatic state. Patients having less than three symptoms were less likely to be diagnosed by any means.

Conclusions: One-third of SARS-CoV-2 infections in our study were asymptomatic. This mandates applying proper measures to prevent transmission even from apparently healthy individuals. Modifiable factors associated with symptomatic infection should be controlled to reduce the risk of COVID-19 complications.