The first ever case of Covid-19 reinfection has been recorded in the world as a 33-year-old man from Hong Kong has tested positive for the virus for the second time, four months after his initial recovery in April.

The virus was detected at an airport upon the man's return from Europe to Hong Kong where he was screened. This is the world's first documentation of a patient who recovered from Covid-19, but got another episode of Covid-19 afterwards, researchers mentioned in an emailed statement. This came across as a shock to several scientists and health officials as the man is expected to have developed immunity following his recovery from the infection in April. "Our findings suggest that SARS-CoV-2 may persist in humans. The findings also suggest SARS-CoV-2 is reminiscent of the coronaviruses that cause the common cold, and may continue to circulate even if patients have acquired immunity via natural infection or via vaccination," according to a team of researchers.

Corey Smith, head of translational and human immunology at the QIMR Berghofer Medical Research Institute in Brisbane, mentioned in a statement that it would be difficult to identify people who have been reinfected if they did not show any symptoms. "Because he showed no symptoms on the second infection, it is likely that, although the virus has managed to establish infection, his memory immune response has likely prevented any symptomatic disease. This does suggest that natural infection may provide protection against disease, but not reinfection," he reportedly said. Meanwhile, a virologist at Cornell University stated, "The majority of patients likely have a cocktail of immune responses that activate on second exposure. This Hong Kong patient also seems to have been asymptomatic on second infection, perhaps due to some immune response."

The exact reason behind the rare occurrence is yet to be ascertained. Covid-19 has claimed the lives of more than 817,625 people and infected over 23,838,300 people across the world. The virus was first identified in Wuhan, Hubei Province, in China. As the death toll and overall cases began rising rapidly across the world, the World Health Organization (WHO) declared a global health emergency and the outbreak has now been labelled a pandemic. India has recorded 31,70,942 confirmed COVID-19 cases and 58,570 deaths. Maharashtra, Tamil Nadu and Andhra Pradesh have reported the highest number of cases in the country.