A reinfection case of a 33 year old man in Hong Kong has reignited the debate on whether true reinfection can occur. Scientists have confirmed the second infection was caused by a genetically distinct virus from the one that caused the first infection in March. The patient had developed cough and sputum, and was also down with sore throat, fever and headache for three days when he first tested positive for Covid-19. He however remained asymptomatic when he got reinfected in August.
Studies show that following infection with Sars-CoV2, the virus that causes Covid-19, the infected person produces neutralising antibodies rapidly, but the antibody count begins to decline in about one to two months after acute infection. However, prolonged low-grade viral shedding detectable by reverse transcription-polymerase chain reaction tests has led to people testing positive weeks after recovering.
Scientists clarified that the repeated positive tests picked up dead viruses from past infection that did not make the person ill or infected others. The genetic confirmation in Hong Kong proved a second infection can occur, however, there are no reports of people developing symptoms or falling sick the second time.
Dr Anurag Agrawal, director, Council of Scientific and Industrial Research-Institute of Genomics and Integrative Biology, said, “We are now beginning to see cases of re-infection, but still now we have not had a true re-infection where a person was symptomatic the first time, and symptomatic the second time. We only have cases of symptomatic the first time, and asymptomatic the second time. True reinfection with a patient who is twice symptomatic has not yet occurred.”
The amount of live virus in the nose and throat drops significantly soon after Covid-19 symptoms develop, with the duration of infectiousness in most people not lasting more than 10 days after symptoms begin, and 20 days on average in people with severe illness or those who are severely immuno-compromised, according to the US Centers for Disease Control and Prevention.
