Can a patient diagnosed with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) be infected again? This question is still unsolved. We tried to analyze local and literature cases with a positive respiratory swab after recovery. We collected data from symptomatic patients diagnosed with SARS-CoV-2 infection in the Italian Umbria Region that, after recovery, were again positive for SARS-CoV-2 in respiratory tract specimens. Samples were also assessed for infectivity in vitro. A systematic review of similar cases reported in the literature was performed. The study population was composed of 9 patients during a 4-month study period. Among the new positive samples, six were inoculated in Vero-E6 cells and showed no growth and negative molecular test in culture supernatants. All patients were positive for IgG against SARS-CoV-2 nucleoprotein and/or S protein. Conducting a review of the literature, 1350 similar cases have been found. The presumptive reactivation occurred in 34.5 days on average (standard deviation, SD, 18.7 days) after COVID-19 onset, when the 5.6% of patients presented fever and the 27.6% symptoms. The outcome was favorable in 96.7% of patients, while the 1.1% of them were still hospitalized at the time of data collection and the 2.1% died. Several hypotheses have been formulated to explain new positive respiratory samples after confirmed negativity. According to this study, the phenomenon seems to be due to the prolonged detection of SARS-CoV-2 RNA traces in respiratory samples of recovered patients. The failure of the virus to replicate in vitro suggests its inability to replicate in vivo.

Anna Gidari¹, Marco Nofri¹, Luca Saccarelli², Sabrina Bastianelli¹, Samuele Sabbatini³, Silvia Bozza³, Barbara Camilloni³, Igino Fusco-Moffa⁴, Claudia Monari³, Edoardo De Robertis², Antonella Mencacci³, Daniela Francisci¹ 

Anna Gidari and Marco Nofri contributed equally to this work.

* Anna Gidarianna.gidari@studenti.unipg.it

¹ Department ofMedicine, Clinic of Infectious Diseases, “SantaMariadella Misericordiaâ€� Hospital, University of Perugia, Perugia, Italy

² Department of Anesthesiology, Intensive Care and Pain therapyCenter, “Santa Maria della Misericordiaâ€� Hospital, University ofPerugia, Perugia, Italy

³ Department of Medicine, Medical Microbiology Section, Universityof Perugia, Perugia, Italy

⁴ Department of Prevention, Local Health Unit Umbria 1, TravelMedicine Unit, Perugia, Italy

European Journal of Clinical Microbiology & Infectious Diseases

Volume 39, issue 10, October 2020