key: cord-275556-798oed8n
authors: Piubelli, Chiara; Deiana, Michela; Pomari, Elena; Silva, Ronaldo; Bisoffi, Zeno; Formenti, Fabio; Perandin, Francesca; Gobbi, Federico; Buonfrate, Dora
title: Overall decrease of SARS-CoV-2 viral load and reduction of clinical burden: the experience of a Northern Italy hospital
date: 2020-10-12
journal: Clin Microbiol Infect
DOI: 10.1016/j.cmi.2020.10.006
sha: 
doc_id: 275556
cord_uid: 798oed8n

OBJECTIVES: 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 at evaluating a possible association between the severity of clinical manifestations and viral load over time, during the epidemiological transition from high to low transmission setting. METHODS: 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. RESULTS: The proportion of patients requiring intensive care significantly reduced from 6.7% (19/281) in March, to 1.1% (1/86) in April, and to none in May (Fisher’s test p-value=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). CONCLUSIONS: We observed a reduction over time of 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 setting, people are presumably exposed to a lower viral load, which has been previously associated to less severe clinical manifestations.

The proportion of patients requiring intensive care significantly reduced from 6.7% ( We observed a reduction over time of the proportion of patients with Covid-19 requiring intensive 46 care, along with decreasing median values of viral load. As the epidemiological context changes 47 from high to low transmission setting, people are presumably exposed to a lower viral load, which 48 has been previously associated to less severe clinical manifestations. 

Of course, other factors might have had an influence on the decrease of severe cases, such as stricter 119 adherence to quarantine of the most fragile groups of people (i.e. those with chronic conditions, the 120 elderly). In our cohort, median age increased from March to April, but older age has been 121 associated to a worse outcome [10], so we suppose that this factor might not have a major role in 122 our findings. Conversely, the relevance of the transmission setting seems plausible, and efforts 

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