LC, PB, APC, BT, MC, GL, ACP, LR, AM and FC collected the data and performed the serological survey
LC, PB, APC, BT, MC, GL, ACP, LR, AM and FC collected the data and performed the serological survey. men and 4-hydroxyephedrine hydrochloride women (8.3% vs 7.3%, p=0.3), whereas a higher prevalence was observed among foreign-born workers (27/186, 14.5%, p<0.001), employees younger than 30 (64/668, 9.6%, p=0.02) or older than 60 years (38/383, 9.9%, p=0.02) and among healthcare assistants (40/320, 12.5%, p=0.06). Working as frontline HCWs was not associated with an increased frequency of positive serology (p=0.42). A positive association was found with presence and 4-hydroxyephedrine hydrochloride number of symptoms (p<0.001). The symptoms most frequently associated with a positive serology were taste and smell alterations (OR 4.62, 95%?CI: 2.99 to 7.15) and fever (OR 4.37, 95%?CI: 3.11 to 6.13). No symptoms were reported in 84/309 (27.2%) HCWs with positive IgG levels. Declared exposure to a suspected/confirmed case was more frequently associated (p<0.001) with positive serology when the contact was a family member (19/94, 20.2%) than a patient or colleague (78/888, 8.8%). Conclusions SARS-CoV-2 contamination occurred undetected in a large fraction of HCWs and it was not associated with working in COVID-19 frontline areas. Beyond the hospital setting, exposure within the community represents an additional EDNRB source of contamination for HCWs. Keywords: occupational & industrial medicine, 4-hydroxyephedrine hydrochloride virology, diagnostic microbiology, public health Strengths and limitations of this study The serological test employed in our study has, after >15 days from the infection, a declared sensitivity of 97.4% and a specificity of 98.5%. We performed our study on a large cohort of healthcare workers, from an area with a high incidence of COVID-19. Our study was monocentric and performed in Italy, therefore the results may be applicable only to similar scenarios (eg, Western countries with public health system). Introduction As of January 2021, the ongoing pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has affected more than 100?million people worldwide resulting in more than 2?million deaths.1 Since the beginning of the pandemic, healthcare workers (HCWs) have been identified as a group at high risk of infection.2 The occurrence of nosocomial transmission of SARS-CoV-2 has been well described, emphasising the adherence to infection control measures among HCWs to protect themselves and avoid nosocomial outbreaks.2C5 Conversely, other studies did not find differences in SARS-CoV-2 infection rates between frontline and non-frontline HCWs and between HCWs and the general population, suggesting community over nosocomial acquisition as major source of infection.6C8 In the current pandemic scenario, the optimal method to screen HCWs is still under debate. At present, the most frequently employed testing strategy is the detection of SARS-CoV-2 RNA through reverse transcriptase PCR on upper respiratory specimens in symptomatic individuals or in those exposed to confirmed cases of COVID-19. Unfortunately, the testing strategy based solely on upper respiratory specimens has significant limitations. In a large meta-analysis, the rate of positive nasopharyngeal swabs (NPS) ranged from 25% to 80% and decreased with time and in asymptomatic or pauci-symptomatic cases.9 Of note, no data on test sensitivity in asymptomatic infected individuals exists, and clinical symptoms of COVID-19 among infected HCWs are often relatively mild, with fever and dyspnoea reported in 38% to 60%?and 13% to 47% of cases, respectively.2 3 7 8 10 It is also not uncommon for HCWs to work with 4-hydroxyephedrine hydrochloride mild symptoms,8 4-hydroxyephedrine hydrochloride 11 which increases the hazard of nosocomial outbreaks. More recently, the serological assessment of SARS-CoV-2 infection has been proposed as screening strategy among both HCWs and the general population. Antibody sensitivity is 30% 1?week after symptoms onset and rises to 70% and >90% at 2 and 3 weeks, respectively.12 Hence, the most useful role for serology consists in detecting previous.