High prevalence of symptoms among Brazilian subjects with antibodies against SARS-CoV-2

Ana M B Menezes,Cesar G Victora,Fernando C Barros,Lúcia C Pellanda,Marilia A Mesenburg,Fernando C Wehrmeister,Pedro C Hallal,Odir A Dellagostin,Cláudio J Struchiner,Mariângela F Silveira,Fernando P Hartwig,Marcelo N Burattini,Aluísio J D Barros,Bernardo L Horta

doi:10.1038/s41598-021-92775-y

Abstract

Since the beginning of the pandemic of COVID-19, there has been a widespread assumption that most infected persons are asymptomatic. Using data from the recent wave of the EPICOVID19 study, a nationwide household-based survey including 133 cities from all states of Brazil, we estimated the proportion of people with and without antibodies for SARS-CoV-2 who were asymptomatic, which symptoms were most frequently reported, number of symptoms and the association with socio-demographic characteristics. We tested 33,205 subjects using a rapid antibody test previously validated. Information was collected before participants received the test result. Out of 849 (2.7%) participants positive for SARS-CoV-2 antibodies, only 12.1% (95% CI 10.1–14.5) reported no symptoms, compared to 42.2% (95% CI 41.7–42.8) among those negative. The largest difference between the two groups was observed for changes in smell/taste (56.5% versus 9.1%, a 6.2-fold difference). Changes in smell/taste, fever and body aches were most likely to predict positive tests as suggested by recursive partitioning tree analysis. Among individuals without any of these three symptoms, only 0.8% tested positive, compared to 18.3% of those with both fever and changes in smell or taste. Most subjects with antibodies against SARS-CoV-2 are symptomatic, even though most present only mild symptoms.

Highlights

Since the beginning of the pandemic of COVID-19, there has been a widespread assumption that most infected persons are asymptomatic
Population-based studies are relevant for studying SARS-CoV-2 symptoms, because asymptomatic patients or those with mild symptoms may be identified at home, rather than in health service-based studies
Symptoms had only been assessed for those with positive tests, and the information was collected after the individual had learned about the test result

Summary

Introduction

Since the beginning of the pandemic of COVID-19, there has been a widespread assumption that most infected persons are asymptomatic. Using data from the recent wave of the EPICOVID19 study, a nationwide household-based survey including 133 cities from all states of Brazil, we estimated the proportion of people with and without antibodies for SARS-CoV-2 who were asymptomatic, which symptoms were most frequently reported, number of symptoms and the association with socio-demographic characteristics. Among individuals without any of these three symptoms, only 0.8% tested positive, compared to 18.3% of those with both fever and changes in smell or taste. Using data from the most recent wave of the EPICOVID19 study, a nationwide household-based survey including 133 cities from all states of B razil[7], we estimate the proportion of people with and without antibodies for SARS-CoV-2 who were asymptomatic. We performed conditional inference tree analyses using binary recursive partitioning to identify which combinations of symptoms were most likely to predict positive test results

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