Man recovers from Covid-19, contracts it again 10 days later

Just 10 days after being discharged from hospital he needed intensive care again.

The case was published in The American Journal of Emergency Medicine, detailing how the unidentified man ended up on a ventilator after his lungs began to fail but recovered after 39 days at hospital. He tested positive for the Covid-19 again.  
According to the reports in Daily Mail, the elderly man was already suffering from Parkinson's, diabetes, chronic kidney disease and high blood pressure when he was first diagnosed with Covid-19. He had a high fever for a week following which he was admitted to the Massachusetts General Hospital where his condition deteriorated and was put on a ventilator. He was discharged after he tested negative twice for Covid-19.
But just 10 days later, the man again developed a fever and struggled to breathe. His chest X-ray showed signs of Covid-19 infection in his lungs again, and a swab test again confirmed he was positive. He was admitted to intensive care and went into a shock and his kidneys failed, but he again survived, recovered and was sent back to a normal ward after a week.
In the article titled 'A case report of possible novel coronavirus 2019 reinfection', medics are trying to ascertain whether people can catch the coronavirus twice, type of immunity patients build up against Covid-19 and for how long they are immune. 
The doctors, led by Dr Nicole Duggan, said, "Many viruses demonstrate prolonged presence of genetic material in a host even after clearance of the live virus and symptomatic resolution. Thus, detection of genetic material by [swab test] alone does not necessarily correlate with the active infection or infectivity."
Dr Duggan added, "Observational data suggest SARS-CoV-2 viral shedding may last 20-22 days after symptom onset on average with some outlying cases exhibiting shedding as long as 44 days."