A highly transmissible Covid-19 variant that emerged in Brazil and has now been found in at least 20 countries can re-infect people who previously recovered from the disease, Reuters quoted scientists as saying on Tuesday.

In a study of the mutant virus's emergence and its spread in the Amazon jungle city of Manaus, the scientists said the variant — known as P.1 — has a “unique constellation of mutations” and had very rapidly become the dominant variant circulating there.

Out of 100 people in Manaus who had previously recovered from infection with the coronavirus, “somewhere between 25 and 61 of them are susceptible to re-infection with P.1,” said Nuno Faria, a virus expert at Imperial College London, who co-led the research which has not yet been peer reviewed.