Though there have been at least three cases in the city of a person testing positive for COVID-19 for a second time, doctors who handled two of these patients admitted they were not confirmed reinfections as genome study was not done. Experts have frequently reiterated that chances of reinfections are rare.
A police officer had allegedly tested positive for a second time in July at Indraprastha Apollo Hospital. But Rajesh Chawla, a senior consultant at the hospital, said that they cannot call it a reinfection.
“The policeman came to us in July with fever and sore throat and he was tested positive for the virus. He had earlier tested positive more than a month ago at another hospital. It is difficult to say whether it was reinfection or the same infection. Now studies are saying that viral particles can persist for up to 140 days,” Dr. Chawla said.
“We did the genome study of the virus when he came to our hospital the second time. But it was not done when he was first infected. If it had been done, then we could have confirmed whether it was indeed a reinfection.” he added.
Chandra Goda, HoD of Medical Oncology Department of Aakash Healthcare, who also treated a patient who tested positive for a second time after recovering, had a similar opinion. “But the patient had tested negative after testing positive for the time and then her health improved. But she tested positive again and her health deteriorated. Which means that it could be a reinfection, but we cannot confirm it as Next Generation Sequencing [NGS], which is a genetic study of the virus. It was not done both the times she tested positive,” he said.
How to confirm?
K. Srinath Reddy, epidemiologist and president of Public Health Foundation of India (PHFI) in Delhi, said that reinfection is rare.
“When the virus leaves a person’s body, it carries a bit of her genetic material. The virus has a genetic structure, but it also picks up fragments of the host’s genetic material. A reinfection can be confirmed if a genome study of the virus is done and the genetic structure of the virus is different at the two different points when she tested positive,” Dr. Reddy said.
He said that if the genetic structure is the same, then it is not a reinfection and could be a dead virus. The expert said that even if a person had COVID-19 and has antibodies and memory cells against the virus, it can invade the body and reach the nose or throat.
“During this time, the person will test positive for COVID-19, if he takes a nasal swab test. But in most cases, people will have memory cells to fall back upon to mount an immune response to prevent infection from turning into a disease,” Dr. Reddy added.