Time length of negativization and cycle threshold values in 182 healthcare workers with COVID-19 in Milan, Italy: An observational cohort study

Lisa Cariani, Beatrice Silvia Orena, Federico Ambrogi, Simone Gambazza, Anna Maraschini, Antonella Dodaro, Massimo Oggioni, Annarosa Orlandi, Alessia Pirrone, Sara Uceda Renteria, Mara Bernazzani, Anna Paola Cantù, Ferruccio Ceriotti, Giovanna Lunghi

Research output: Contribution to journalArticlepeer-review

Abstract

Background: Coronavirus Disease 2019 (COVID-19) has rapidly spread worldwide, becoming an unprecedented public health emergency. Rapid detection of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) suspected cases is crucial to control the spread of infection. We aimed to evaluate the time length of negativization from the onset of symptoms in healthcare workers (HCWs) with COVID-19, and to evaluate significant variations in cycle threshold (CT) values and gene positivity (E, RdRP, and N genes) among positive individuals who returned to work. Methods: We retrospectively analyzed a consecutive cohort of 182 SARS-CoV-2-positive HCWs in Milan, from 16 March to 30 April 2020. Nasopharyngeal swabs were tested by RT-PCR. Results: Asymptomatic HCWs were 17.6% (32/182), and 58 healed at 30 April 2020. The median time length of negativization was 4 weeks (35% of symptomatic versus 40% of asymptomatic HCWs). Four HCWs, healed at 30 April, turned positive within three weeks during controls set up in the work unit. Three-gene positivity had the greatest variability, and increasing CT values from single-to three-gene positivity among all age groups were observed. Conclusions: Self-isolation longer than two weeks and prolonged follow-up periods for the staff returning to work after COVID-19 could be the most suitable choices to counter the SARS-CoV-2 spread. Further studies are needed to investigate infectiousness profiles among positive individuals.

Original languageEnglish
Article number5313
Pages (from-to)1-10
Number of pages10
JournalInternational Journal of Environmental Research and Public Health
Volume17
Issue number15
DOIs
Publication statusPublished - Aug 1 2020

Keywords

  • Coronavirus Disease 2019
  • Cycle Threshold values
  • Health care workers
  • Reverse Transcription PCR
  • SARS-CoV-2

ASJC Scopus subject areas

  • Public Health, Environmental and Occupational Health
  • Health, Toxicology and Mutagenesis

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