Covid-19, SARS, MERS and pandemic influences: comparability of transmissibility, hospitalization and mortality rates

The University of Brescia participates in the international study published in the prestigious Lancet Infectious Diseases magazine.

Brescia, 21 July 2020 – An international study of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID), which sees among the authors Prof. Francesco Castelli, Professor of Infectious Diseases of the University of Brescia and Director of the Operational Unit of Infectious Diseases of the Civil Hospital of Brescia, compares the rates of transmissibility, hospitalization and mortality of acute acute respiratory syndrome due to Coronavirus 2 (SARS-CoV-2), or Covid-19, with the rates of other Coronavirus epidemics such as Syndrome acute respiratory disease (SARS), Middle Eastern respiratory syndrome (MERS) and pandemic viral influences of 1918 and 2009. The study is published in the prestigious journal Lancet Infectious Diseases.

These are the main evidences:

  • the basic reproduction number, or Covid-19’s R0 is comparable to the SARS-CoV R0 and higher than the R0 of the pandemic influence
  • Covid-19 and SARS mortality increases markedly after the age of 70 unlike the pandemic influences of 1918 and 2009
  • the percentage of symptomatic people requiring hospitalization is higher for Covid-19 infections than the 2009 pandemic influence
  • the risk of ICU admission is 5-6 times higher in Covid-19 patients than in patients with 2009 pandemic influence
  • the lethality rate compared to the infected, including those who develop very mild symptoms, probably stands at around 1%; serological studies will help refine this estimate

Transmissibility and basic reproduction number

Covid-19 has the highest average of R0, that is the “basic reproduction number” which represents the average number of secondary infections produced by each infected individual: R0 2.5 against R0 2.4 for SARS-CoV, R0 2.0 for 118 pandemic influence, R0 1.7 for 2009 pandemic influence.

Covid-19 incubation period and viral excretion

All three coronaviruses responsible for Covid-19 (SARS-CoV-2), SARS (SARS-CoV), MERS (MERS-CoV) have a longer incubation period (time from infection to onset of symptoms ) compared to influence viruses. This evidence, together with the fact that people with SARS-Cov-2 eliminate the virus more significantly in the first days of the onset of symptoms (and there is evidence that this may also occur in the days preceding the symptomatic onset) makes it more containment measures are difficult compared to SARS

Mortality rate

The mortality rate in people with Covid-19 increases rapidly with age and deaths occur almost exclusively in people over the age of 50. The study compares the variables and characteristics of the 1918 and 2009 pandemic influences with SARS-CoV-2, SARS-CoV and MERS-CoV.

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