SARS-CoV-2 transmission by asymptomatic healthcare workers positive to screening swab: an Italian study. (7th September 2022)

• Record Type: Journal Article
• Authors: Palese, Francesca; Arnoldo, Luca; Brunelli, Laura; Buzancic, Silvana; De Giusti, Valentina Anna; Ferrazzano, Alberto; Gallo, Tolinda; Iob, Andrea; Mauro, Katia; Pipan, Corrado; Polonia, Marta; Ruscio, Edoardo; Treleani, Maurizio; Conte, Alessandro
• Is Part Of: European journal of public health. Volume 32:Number 5(2022)
• Page Start: 813
• Page End: 817
• Publication Date: 2022-09-07
• Subjects: Epidemiology -- Europe -- Periodicals; Public health -- Europe -- Periodicals; 362.109405
• DOI: 10.1093/eurpub/ckac121
• Languages: English
• ISSNs: 1101-1262

Abstract

Abstract: Background: SARS-CoV-2 spreads primarily through respiratory droplets of symptomatic individuals. With respect to asymptomatic individuals, there are conflicting results in the literature and a lack of studies specifically examining transmission in healthcare settings. Methods: The aim of this retrospective study, conducted in a northeastern Italian region, was to estimate the contagiousness of asymptomatic healthcare workers (HCWs) who tested positive for SARS-CoV-2. Asymptomatic HCWs who tested positive for SARS-CoV-2 by real-time reverse transcription polymerase chain reaction (rRT-PCR) at a regular screening nasopharyngeal or oropharyngeal swab between 1 February 2020 and 15 September 2020 were considered index cases. Contacts who were at high risk of infection and had follow-up swabs were included. Contacts were considered infected if they had a positive follow-up swab and/or symptoms associated with COVID-19 confirmed by a positive test within 14 days of exposure. Information was taken from records previously collected to identify contacts. Infectivity was estimated using the attack rate (AR) with a 95% confidence interval (95% CI). Results: Thirty-eight asymptomatic HCWs who were positive at the screening swab and 778 contacts were identified. Contacts included 63.8% of colleagues, 25.6% of patients, 7.7% of family members and 3.0% of other contacts. Seven contacts tested positive for SARS-CoV-2 (AR: 0.91%, 95% CI: 0.89–0.93). Five of them were family members (AR: 8.3%), one was a colleague (0.2%) and one was a contact of other type (4.2%). Conclusions: Viral spread by asymptomatic HCWs was less than in other settings. Identification of risk factors for transmission and reliable indicators of infectivity would be important to prioritize preventive measures.