COVID-19 severity appears to be reduced in spring/summer

{ 'type': 'article-journal', 'journalAbbreviation': 'E&P', 'author': [ {'family': 'Sposato', 'given': 'Bruno'}, {'family': 'Serafini', 'given': 'Andrea'}, {'family': 'Simoncini', 'given': 'Enrico'}, {'family': 'Croci', 'given': 'Leonardo'}, {'family': 'Guidoni', 'given': 'Chiara'}, {'family': 'Scalese', 'given': 'Marco'}, {'family': 'Baratta', 'given': 'Pasquale'}, {'family': 'Cresti', 'given': 'Alberto'}, {'family': 'Lacerenza', 'given': 'Leonardo Gianluca'}, {'family': 'Lena', 'given': 'Fabio'}, {'family': 'Nencioni', 'given': 'Cesira'}, {'family': 'Spargi', 'given': 'Genni'}, {'family': 'Perrella', 'given': 'Antonio'}], 'issued': {'date-parts': [[2023, 3]]}, 'abstract': 'BACKGROUND: because of different human behaviours, SARS-CoV-2 spread may be lower in ' 'spring/summer. On the contrary, it is not clearly known whether the clinical course/severity ' 'of hospitalized patients infected by SARS-CoV-2 can be different in the various seasons.. ' 'Objectives: to understand whether there were differences in severity of COVID-19 in patients ' 'who had contracted the infection in winter versus those infected in spring/summer. DESIGN: ' 'observational retrospective cohort study. SETTING AND PARTICIPANTS: from the administrative ' 'database of the SARS-CoV-2 surveillance system and that of hospital discharge, a cohort of ' 'patients (8,221, 653 of which were hospitalized) who tested positive to the RT-PCR test for ' 'SARS-CoV-2 between 01.12.2020 and 31.07.2021 in the Grosseto province (Tuscany Region, ' 'Central Italy) was selected and analysed. MAIN OUTCOME MEASURES: hospitalization rate and ' 'length, continuous positive airway pressure (CPAP) or non-invasive ventilation (NIV) use, ' 'Intensive Care Unite (ICU) admissions, intra-hospital mortality and PaO2/FiO2 values were ' 'measured and compared between subjects infected in winter and those who developed COVID-19 in ' 'spring/summer. Viral load (cycle threshold, Ct), vitamin D, serum ferritin, IL-6, ' 'procalcitonin, D-dimer, and C-reactive protein measured in the two periods were also ' 'compared. RESULTS: in the considered months, the hospitalization rate among 8,221 patients ' 'with COVID-19 was 8%: 370 (8.5%) individuals were hospitalized in winter and 283 (7,3%; ' 'p=0.31) in spring/summer; 62 (16.8%), 88 (23.8%), and 63 (17%) in winter and 28 (9.9%), 40 ' '(14.1%), and 36 (12.7%) in spring/summer were admitted in ICU (p=0.01), used CPAP/NIV ' '(p=0.002) and died (p=0.13), respectively. Hospitalization days were 14.5±11.6 in winter and ' '10.3±8.84 in spring/summer (p=0.001), while minimum PaO2/FiO2, measured during hospital stays ' 'was 123.2±38.6 in spring/summer and 112.6±40.8 in winter (p=0.054). Multivariate analysis ' '(adjusted for all confounding factors) also confirmed reduced risks of having ICU admissions ' '(0.53; 95%CI 0.32;0.88; p=0.01) and of using CPAP/NIV (0.48; 95%CI 0.32;0.75; p=0.001) in ' 'spring/summer when compared to winter. Hospitalization days and minimum PaO2/FiO2 were also ' 'lower in spring/summer (β= -3.9; 95%CI -5.5;-2.2; p=0.001) and winter (β= -17; 95%CI ' '-0.93;35; p=0.06), respectively. The adjusted hazard ratio of mortality in winter, obtained ' 'with a Cox model, was higher of about 38% compared to spring/summer. No Ct values (viral ' 'load) differences were found either in winter (19.45±6.18) or spring/summer (20.3±6.7; ' 'p=0.343). IL-6, ferritin, procalcitonin, D-dimer were similar. Conversely, CRP was lower ' 'whereas vitamin D was higher in the warmer seasons. CONCLUSIONS: COVID-19 may be less severe ' 'during spring/summer in hospitalized patients. This does not seem to be influenced by ' 'different SARS-CoV-2 viral load in the different periods considered. C-reactive protein was ' 'found to be lower whereas vitamin D higher in the warmer months. It can be hypothesized that ' 'higher levels of vitamin D in spring/summer, compared to winter, may be associated to a ' 'positive modulation of COVID-19 induced inflammation with a possible disease severity ' 'reduction during spring/summer.', 'container-title': 'Epidemiologia & Prevenzione', 'container-title-short': 'E&P', 'DOI': '10.19191/EP23.1.A503.016', 'ISSN': '1120-9763, 2385-1937', 'issue': '1-2', 'keyword': 'COVID-19; SARS-CoV-2; viral load; severity; inflammation; season; vitamin D', 'medium': 'JB', 'publisher': 'Inferenze scarl', 'publisher-place': 'IT', 'title': 'In primavera/estate la gravità del COVID-19 appare ridotta', 'URL': 'https://doi.org/10.19191/EP23.1.A503.016', 'volume': '47'}