{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T03:02:28Z","timestamp":1760238148675,"version":"build-2065373602"},"reference-count":27,"publisher":"MDPI AG","issue":"15","license":[{"start":{"date-parts":[[2020,7,23]],"date-time":"2020-07-23T00:00:00Z","timestamp":1595462400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["IJERPH"],"abstract":"<jats:p>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.<\/jats:p>","DOI":"10.3390\/ijerph17155313","type":"journal-article","created":{"date-parts":[[2020,7,23]],"date-time":"2020-07-23T10:14:06Z","timestamp":1595499246000},"page":"5313","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Time Length of Negativization and Cycle Threshold Values in 182 Healthcare Workers with Covid-19 in Milan, Italy: An Observational Cohort Study"],"prefix":"10.3390","volume":"17","author":[{"given":"Lisa","family":"Cariani","sequence":"first","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Microbiology Unit, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4921-0757","authenticated-orcid":false,"given":"Beatrice Silvia","family":"Orena","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Microbiology Unit, 20122 Milan, Italy"},{"name":"Specialization School in Microbiology and Virology, University of Milan, 20142 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9358-011X","authenticated-orcid":false,"given":"Federico","family":"Ambrogi","sequence":"additional","affiliation":[{"name":"Laboratory of Medical Statistics and Biometry, Giulio A. Maccacaro, Department of Clinical Sciences and Community Health, Campus Cascina Rosa, University of Milan, 20133 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-6225-2989","authenticated-orcid":false,"given":"Simone","family":"Gambazza","sequence":"additional","affiliation":[{"name":"Laboratory of Medical Statistics and Biometry, Giulio A. Maccacaro, Department of Clinical Sciences and Community Health, Campus Cascina Rosa, University of Milan, 20133 Milan, Italy"},{"name":"UOC Direzione Professioni Sanitarie, Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anna","family":"Maraschini","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Microbiology Unit, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Antonella","family":"Dodaro","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Microbiology Unit, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-2709-6965","authenticated-orcid":false,"given":"Massimo","family":"Oggioni","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Virology Unit, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Annarosa","family":"Orlandi","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Virology Unit, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Alessia","family":"Pirrone","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Microbiology Unit, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-2027-8478","authenticated-orcid":false,"given":"Sara","family":"Uceda Renteria","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Virology Unit, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Mara","family":"Bernazzani","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Responsabile Infermieristico area Direzione Medica di Presidio, Coordinamento dipartimenti clinici, Servizio Prevenzione Igiene Ospedaliera, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Anna Paola","family":"Cant\u00f9","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Direzione Medica di Presidio, 20122 Milan, Italy"},{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Romeo ed Enrica Invernizzi Paediatric Research Centre, Department of Biosciences, University of Milan, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-0958-5354","authenticated-orcid":false,"given":"Ferruccio","family":"Ceriotti","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore, Clinical Laboratory, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Giovanna","family":"Lunghi","sequence":"additional","affiliation":[{"name":"Fondazione IRCCS Ca\u2019 Granda Ospedale Maggiore Policlinico, Virology Unit, 20122 Milan, Italy"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2020,7,23]]},"reference":[{"key":"ref_1","first-page":"11","article-title":"The origin, transmission and clinical therapies on coronavirus disease 2019 (COVID-19) outbreak\u2014An update on the status","volume":"7","author":"Guo","year":"2020","journal-title":"Mil. 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