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.

自 COVID-19 大流行开始以来，人们普遍认为大多数感染者没有症状。利用最近一波 EPICOVID19 研究（一项涵盖巴西各州 133 个城市的全国性家庭调查）的数据，我们估计了有和没有 SARS-CoV-2 抗体的无症状人群的比例，哪些症状最严重经常报告的症状数量以及与社会人口特征的关联。我们使用先前经过验证的快速抗体测试对 33,205 名受试者进行了测试。在参与者收到测试结果之前收集信息。在 849 名 (2.7%) SARS-CoV-2 抗体阳性参与者中，只有 12.1% (95% CI 10.1–14.5) 报告没有症状，而阴性参与者中有 42.2% (95% CI 41.7–42.8) 报告没有症状。两组之间最大的差异是嗅觉/味觉的变化（56.5% 与 9.1%，相差 6.2 倍）。正如递归分区树分析所表明的，嗅觉/味觉、发烧和身体疼痛的变化最有可能预测阳性检测。在没有这三种症状中任何一种症状的人中，只有 0.8% 的人检测呈阳性，而同时发烧且嗅觉或味觉改变的人中，这一比例为 18.3%。大多数携带 SARS-CoV-2 抗体的受试者都有症状，尽管大多数仅表现出轻微症状。