COVID-19-like symptoms and their relation to SARS-CoV-2 epidemic in children and adults of an Italian birth cohort

Abstract Background A number of cases positive for SARS-CoV-2 escape surveillance systems, especially in the first epidemic waves and/or when the number of cases becomes too large to allow complete diagnostic coverage. Methods During the first SARS-CoV-2 epidemic wave hitting Italy in the spring 2020, mothers participating in an Italian NINFEA birth cohort were invited to complete an online questionnaire on COVID-19-like symptoms in the household. We estimated the population prevalence of COVID-19-like symptoms in children and adults, assessed their geographical correlation with the cumulative number of COVID-19 cases by province, analysed their clustering within families, and estimated their sensitivity, positive predictive value (PPV) and negative predictive value (NPV) for COVID-19 diagnosis in individuals tested for SARS-CoV-2.Results Information was collected on 3184 households, 6133 adults, and 5751 children. In the period March-April 2020, 55.4% of the NINFEA families had at least one member with at least one COVID-19-like symptom. There was a strong geographical correlation between the population cumulative incidence of COVID-19 and the prevalence of muscle pain, fatigue, low-grade fever, and breathing difficulties in adults (Spearman’s rho ≥0.70). Having at least one family member with a COVID-19 diagnosis, compared with none tested for SARS-CoV-2, was associated with an increased prevalence ratio (PR) of almost all COVID-19-like symptoms in adults, and only of low-grade fever (37-37.5°C; PR 5.27; 95% confidence intervals: 2.37 to 11.74) and anosmia/dysgeusia in children. Among adults with COVID-19 diagnosis, fatigue, muscle pain, and fever had a sensitivity ≥70%. In individuals tested for SARS-CoV-2, with a 16.6% prevalence of COVID-19, breathing difficulties and nausea/vomiting had the highest PPVs, with point estimates close to 60%, and with NPVs close to 90%.Conclusions The geographical prevalence of COVID-19-like symptoms in adults may inform on local disease clusters, while certain symptoms in family members of confirmed COVID-19 cases could help identify the intra-familial spread of the virus and its further propagation in the community. Low-grade fever is frequent in children with at least one household member with COVID-19 and possibly indicates child infection.