Research

Coronavirus spreads more easily than other viruses

Measures to limit the spread of the coronavirus should have been more stringent because modelling was based on earlier, less transmissible viruses, a new study has indicated. New research, published in The Lancet Infectious Diseases journal, indicates the coronavirus that causes COVID-19 seems to spread far more easily than either severe acute respiratory syndrome (SARS) or Middle East Respiratory Syndrome (MERS), and can be transmitted by people with no symptoms, with “substantial infectivity” during the incubation period.

The analysis, based on contact tracing data from 349 people with COVID-19 and 1,964 of their close contacts in Guangzhou, found people with COVID-19 were at least as infectious before they developed symptoms as during their actual illness.

“Our analyses suggest that the infectiousness of individuals with COVID-19 before they have symptoms is high and could substantially increase the difficulty of curbing the ongoing pandemic”, said Dr Yang Yang from the University of Florida in the USA who co-led the research. Co-author Dr Natalie Dean, also from the University of Florida, said the transmission risk “is around twice what has been estimated for SARS (4.6–8 per cent) and three times higher than for MERS (4–5 per cent), although these data are only based on a small number of studies.” In a linked comment, Dr Virginia Pitzer from Yale School of Public Health noted the “findings confirm the relative importance of pre-symptomatic transmission.”

The World Health Organisation (WHO) relied heavily on evidence from the less prolific SARS and MERS outbreaks when devising its guidance on physical distancing and other preventive measures. Critics say this led to an underestimation of the protections required, including PPE and physical distancing rules.
Read more: Qin-Long Jing, et al. Household secondary attack rate of Covid-19 and associated determinants in Guangzhou, China: a retrospective cohort study, [Full text] The Lancet Infectious Diseases, online first, 17 June 2020. Migrant Clinicians Network blogSource: Risks 953

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