A survey on the frequency of COVID-19-like symptoms on students and staff of the University of Milan

A survey was conducted through a web link on the students and staff of the Università degli Studi di Milano, Italy in the period 14-30 April 2020. It was anonymous at the source and included history of COVID-19-related questions (fever, headache, cold, cough, anosmia, gastrointestinal complaints and separately fever over 38.5°C) in the previous three weeks, and similar information on cohabitants. A total of 14 374 subjects were included. Overall, from 24 March to 30 April, 3138 subjects (21.8%) reported COVID-19-like symptoms, and 219 (1.5%) fever above 38.5°C; 217 subjects performed at least one swab. Of these, 46 were positive (21.3% of those performed, 0.3% of the total). The frequency of any symptom was similar in women and men, but fever above 38.5°C was lower in women (multivariate odds ratio (OR) = 0.65, 95% confidence interval, CI, 0.49-0.85). There was a strong association between symptoms in the respondent and in cohabitants: 64% of subjects with symptoms reported at least one cohabitant with symptoms, compared to 14% of asymptomatic subjects (OR = 11.4, 95% CI, 10.4-12.6). The lower risk of serious symptoms in women, and the strong intra-nucleus of cohabitation contagiousness are an indication that at least part of the symptoms was caused by a new pathogen - SARS-CoV-2. These data, therefore, suggest that the number of persons affected by COVID-19 was much greater in northern Italy than the number of recorded cases. This has implications for the prevention, management and mortality of other serious diseases, including cancer.