Almost 80% of coronavirus patients caught the respiratory disease from someone who wasn’t showing any symptoms, a new study suggests.
Researchers also found that a person can have the virus for 3.8 days before becoming symptomatic and still be able to infect others.
The team from the Shanghai Jiao Tong University School of Medicine said their results indicated that isolation alone is not enough to slow the spread, and has to be coupled with rigorous testing and contact tracing.
Using data from China, they used mathematical modelling to estimate on average how long it was taking for people in Wuhan and outside the city to contract Covid-19.
Residents in Wuhan have finally been able to go outside 76 days after draconian measures were imposed to halt the spread of coronavirus.
Anyone with a green QR code on a smartphone health app may now exit the city that once was the Covid-19 epicentre.
The research team found that 79.7% of people caught the bug from someone who appeared perfectly healthy with no symptoms, but had already been infected, MailOnline reported.
They wrote:
Through several different approaches, we achieve largely consistent results: a large portion of Covid-19 transmissions may happen presymptomatically.
The researchers added that patients were ‘likely to become infectious in the early stage of their infections instead of just before their symptom onsets’.
However, they stressed that the findings should be interpreted with caution’ because ‘the epidemic data is very limited, adding: ‘Therefore both estimations of the incubation period and the serial interval of Covid-19 have considerable uncertainty.’
Limitations included the fact cases with severe symptoms were more likely to be detected, and cases with clearly traced contacts were likely to come from areas with lots of public health resources.
The team said
aggressive testing, isolation of close contacts and social distancing to prevent presymptomatic or asymptomatic transmissions are crucial’ to tackling coronavirus.
