Chinese researchers have warned of a new mutated version of coronavirus that could infect people for nearly two months.
Chinese military researchers found a middle-aged man who had the disease for 49 days, which is significantly longer than other durations of illness, according to reports.
He needed to be treated with a plasma transfusion from other COVID-19 sufferers who had recovered, it's claimed.
Previous research showed patients who survived the virus normally tested negative after 20 days on average, with the longest previous case at 37 days.
But despite the length of his illness the Chinese patient, who has not been named, had only relatively mild symptoms.
He had infected lesions to his lungs which disappeared shortly after he was taken to hospital.
Researchers said the patient's case might be 'chronic', which could suggest coronavirus has mutaed.
The researchers from the Army Medical University in Chongqing, No 967 Hospital of PLA, Dalian, and General Hospital of the PLA Central Theatre Command in Wuhan said that the virus may have formed a 'symbiotic relationship' with its host.
Reports state one of the patient's elderly female relatives also tested positive for COVID-19, with moderate symptoms.
Despite having pre-existing conditions she reportedly recovered quicker recovery than average for her age.
The researchers said that this information could point towards a new mild sub-type of COVID-19 which while not as transmissible could be harder to eliminate.
They warned that other "chronic" patients who would not be treated because of their mild symptoms could continue to spread the infection and cause a fresh outbreak.