Studies show people with the coronavirus are most infectious just at the point when they first begin to feel unwell, World Health Organization (WHO) experts said on Tuesday.

This feature has made it so hard to control spread of the virus that causes COVID-19 disease, but it can be done through rigorous testing and social distancing, they said.

“It appears from very limited information we have right now that people have more virus in their body at or around the time that they develop symptoms, so very early on,” Maria van Kerkhove, a WHO epidemiologist and technical lead on the pandemic, told a live session on social media.

Preliminary studies from Germany and the United States suggest that people with mild symptoms can be infectious for up to 8-9 days, and “it can be a lot longer for people who are more severely ill”, she said.

Earlier, some disease experts questioned her statement on Monday that transmission of COVID-19 by people with no symptoms is “very rare”, saying this guidance could pose problems for governments as they seek to lift lockdowns.

Van Kerkhove, citing disease-modelling studies, clarified on Tuesday that some people do not develop symptoms, but can still infect others.

https://uk.reuters.com/article/uk-health-coronavirus-who-symptoms/coronavirus-patients-most-infectious-when-they-first-feel-unwell-who-idUKKBN23G22Z