Overall decrease in SARS-CoV-2 viral load and reduction in clinical burden: the experience of a hospital in northern Italy

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In Italy the burden of patients with coronavirus disease 2019 (COVID-19) gradually decreased from March to the end of May. In this work we aimed to evaluate a possible association between the severity of clinical manifestations and viral load over time during the epidemiological transition from high-to low-transmission settings.|We reviewed the cases of COVID-19 diagnosed at the emergency room of our hospital, retrieving the proportion of patients admitted to the intensive care unit. A raw estimation of the viral load was done evaluating the Ct (cycle threshold) trend obtained from our diagnostic reverse transcriptase real-time PCR test.|The proportion of patients requiring intensive care significantly decreased from 6.7% (19/281) in March to 1.1% (1/86) in April, and to none in May (Fisher's test p 0.0067). As for viral load, we observed a trend of Ct increasing from a median value of 24 (IQR 19-29) to 34 (IQR 29-37) between March and May, with a statistically significant difference between March and April (pairwise Wilcoxon test with stepdown Bonferroni adjustment for multiple testing, p 0.0003).|We observed a reduction over time in the proportion of patients with COVID-19 requiring intensive care, along with decreasing median values of viral load. As the epidemiological context changes from high-to low-transmission settings, people are presumably exposed to a lower viral load which has been previously associated with less severe clinical manifestations.
Original languageEnglish
Pages (from-to)131.e1-131.e3
JournalClinical Microbiology and Infection
Issue number1
Publication statusPublished - Oct 11 2020


  • Aged Aged, 80 and over COVID-19 COVID-19 Testing Emergency Service, Hospital Female Hospitals Humans Intensive Care Units Italy Male Middle Aged Pandemics Reverse Transcriptase Polymerase Chain Reaction SARS-CoV-2 Severity of Illness Index Viral Load COVID-19 Coronavirus Coronavirus disease 2019 SARS-CoV-2 Viral load


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