A team of American scientists from the Broad Institute analyzed the viral load in hospitalized patients with Covid-19, as well as in asymptomatic carriers of the coronavirus. The results of the work are published on the preprints website medRxiv.org (the study has not yet been reviewed).
One of the main problems of the Covid-19 pandemic is the huge number of asymptomatic patients. The spread of SARS-CoV-2 in people who do not show clinical signs of infection makes it difficult for the healthcare system to fight the coronavirus disease and make timely diagnoses.
Until now, the distribution of viral load (a measure of the severity of infection, which is calculated by assessing the number of viral particles in a given volume of body fluid of an infected organism) in symptomatic and non-symptomatic people has remained uncertain. Meanwhile, this is what will help to fully assess the risks of transmission of the virus.
The new study was conducted with the participation of residents and staff of most nursing homes and some similar institutions in Massachusetts. “From April 9 to June 9, 2020, we tested nasopharyngeal swabs from 32,480 people. <…> In addition, we extracted RNA and tested it for SARS-CoV-2 using reverse transcription-polymerase chain reaction. <…> A total of 2,654 nursing home residents (15.5%) and 624 employees (4.1%) tested positive for SARS-CoV-2. SARS-CoV-2 was identified in 12.7% of residents and 3.7% of staff without symptoms, compared with 53.1% of residents and 18.2% of staff with symptoms, ”the authors write.
According to the large-scale analysis, the scientists report that patients with symptoms or without them who were tested found “remarkably similar distributions of viral load.” Moreover, the similarities were most noticeable precisely during the peak of the epidemic in Massachusetts.
“Collectively, the distribution of viral load was very similar, with statistically but not significantly different mean, between symptomatic and symptomatic populations over time, across all subcategories studied (age, race, ethnicity, gender, resident/staff). The mean values were indistinguishable between these groups during the peak of the outbreak in Massachusetts, but the gap appeared later, during the survey period towards the end of May when the epidemic began to subside, ”the scientists note.