Viral load in symptomatic and asymptomatic patients infected with SARS-CoV-2. What have we learned?

Asymptomatic and presymptomatic patients played a critical role in the maintenance and spread of infection during COVID pandemic. However, conflicting views about the infectiousness of asymptomatic patients have been raised.

Identification of asymptomatic cases relies on SARS-CoV-2 genome detection and, in the absence of common epidemiological variables, quantification of viral load (VL) has been proposed as an estimator for SARS-CoV-2 transmission.

Comparison of VLs from symptomatic and asymptomatic patients displayed variable results according to the studied population, the experimental design and the sampling, among other variables.

The aim of this work was to determine VLs in symptomatic and asymptomatic patients at the time of sampling and to retrospectively determine their relationship with severity of disease and other parameters that affected the course of COVID-19, in two towns located in Buenos Aires, Argentina.

Results from our study showed that VLs from symptomatic and asymptomatic patients were significantly different when analyzed globally. In addition, significant differences were found when VLs from each COVID-19 wave were analyzed. In the first wave VLs from asymptomatic patients (log10 8,21 gc/µl) were significantly higher than in symptomatic ones (log10 6,51 gc/µl) while; in the second wave, VLs from asymptomatic patients resulted significantly lower than in symptomatic patients (log10 4,51 gc/µl and log10 5,23 gc/µl, respectively). In the third wave, no significant differences were observed between VLs from both types of patients.

Results from this work demonstrated that the screening of both symptomatic and asymptomatic patients was of utmost importance in order to reduce SARS-CoV-2 transmission to communities.