Europe 1 with AFP 4:17 p.m., April 22, 2022

A patient who tested positive for Covid-19 remained so for 16 months, or 505 days, until his death.

It became the longest known case of infection, according to a study devoted to the evolution of the virus in immunocompromised patients.

The patient, whose identity has not been revealed, had first tested positive in mid-2020.

A patient who tested positive for Covid-19 remained so for 16 months until his death, the longest known case of infection, according to a study devoted to the evolution of the virus in immunocompromised patients.

The patient, whose identity has not been revealed, had first tested positive in mid-2020 and had breathing problems.

He remained positive in all tests - around 45 - until his death 505 days later, Dr. Gaia Nebbia, co-author of the study, told AFP on Friday.

This is the longest known case of Covid infection, according to a press release from the European Congress of Microbiology and Infectious Diseases, which is being held in Lisbon from April 23 to 26 and where the study will be presented.

One patient had up to 10 disease variants

The study, led by researchers from

King's College London and

Guy's and St Thomas'

Hospital London

, looked between March 2020 and December 2021 at nine immunocompromised patients with persistent infection with the virus.

All were positive for at least eight weeks, two were positive for more than a year.

Of the nine patients, four died and four eventually recovered.

A last patient was still infected at the start of 2022, 412 days after being tested positive for the first time.

"Immunocompromised patients with persistent infection have little chance of survival, and new treatment strategies are urgently needed to end their infection," said Gaia Nebbia.

The study aimed to study the mutations of the virus in infected patients for months.

In one of the patients, the virus carried 10 mutations that appeared separately in several major variants, including Alpha, Gamma and Omicron.

According to a study, 70% of Britons have had Covid

"We wanted to characterize the viral evolution in these individuals who could accumulate mutations during their persistent infection. This is one of the hypotheses for the emergence of variants", explains Ms Nebbia.

She points out that mutations of the virus were observed in five of the nine patients.

According to estimates from the National Statistics Office published on Friday, 38.5 million people had Covid in England between the end of April 2020 and mid-February 2022, or 70% of the population.