Scientists in Hong Kong have reported the first documented case of coronavirus re-infection, casting doubt on the idea that lasting immunity against the deadly disease can be achieved.

The groundbreaking revelation was made by a research team with the Hong Kong University (HKU) on Monday. The scientists “have proven the first instance of human re-infection” by the coronavirus, the university’s Faculty of Medicine said.

The dreaded disease was caught twice by an unlucky local resident, described as a 33-year-old man of good health. The patient was first diagnosed with coronavirus late in March, when he had shown the symptoms for three days. The man was discharged from a hospital in mid-April, after twice testing negative for the virus.

“During the second asymptomatic episode of Covid-19, the patient was returning to Hong Kong from Spain via the United Kingdom,” the research paper, accepted by the international medical journal Clinical Infectious Diseases, reads.

“The team showed that the genome sequence of the virus strain in the first episode of COVID-19 infection is clearly different from the genome sequence of the virus strain found during the second episode of infection,” the researchers said.

Our findings suggest that [Covid-19] may persist in the global human population as is the case for other common-cold associated human coronaviruses, even if patients have acquired immunity via natural infection.