In what is being touted as the first case of COVID-19 reinfection in Bengaluru, a private hospital stated that a 27-year-old woman, who was discharged in the month of July after recovering from the disease, tested positive for the coronavirus once again.
Following the news, the Karnataka government has ordered a clinical study on reinfection cases after concerns raised by experts in a high-level meeting with the Medical Education Minister.
The Case
In the statement, Dr Pratik Patil, Consultant, Infectious Diseases, Fortis Hospital, Bannerghatta Road (the hospital in question), said, “In the first week of July, the patient was symptomatic (fever, cough and sore throat) and was tested positive. She was admitted at the hospital and recovered well. A repeat test was conducted on her, which turned out to be negative, post which she was discharged on 24 July.”
“However, nearly after 1 month, in the last week of August, she developed mild symptoms again and has been tested positive again. Both the times she did not have severe disease. This is possibly the first reported case of COVID-19 reinfection in Bangalore.”Dr Pratik Patil
Experts, however, have questioned the basis of the reinfection claim in this particular case, because genome sequencing hasn’t been conducted - a process that was performed in the reinfection case of Hong Kong, for instance, to show that the peron was infected with two different genetic variants of SARS-CoV-2, indicating the two were unrelated.
In the absence of such data, is it possible that the woman tested positive merely because of the lingering viral fragments that may remain in a recovered person?
FIT spoke to Dr Pratik Patil from the concerned hospital to understand the reasons why he thinks this is a likely case of reinfection and not one of remaining viral fragments from the first infection.
‘Strong Clinical Possibility of Reinfection’
Dr Patil starts off by clarifying that genome sequencing and comparison between the first and the second infection would not be possible because unfortunately, the first sample isn’t available.
“The only thing that is pending right now is the viral culture of the second sample, for which we have sent out a mail to National Institute of Virology, but haven’t received a reply so far. I strongly feel that the available information that we have, in terms of antibodies, shows that it is a case of reinfection. I doubt the genome analysis would have changed that.”Dr Pratik Patil
There was no baseline test for IgG antibodies after the first recovery. Antibodies against the novel coronavirus, from what is known so far, start developing by day 12 or 15 and last for 2-3 months, he explains. The woman’s second diagnosis came 52 days after the first, but the antibody test done after the first infection and during the initial phase of the second bout of infection, revealed that she had not developed an antibody response.
Until the last such check that was done on 2nd September, she had tested negative for antibodies from tests done at two different labs.
“If someone has IgG antibodies and develops a second infection, then it can be presumed that they are immune to the first kind of virus and infected by a different one this time.”
“But in this situation, she hasn’t developed either IgM or IgG antibodies. Her body did not mount an immune response, so it could be the first type of virus striking again as well. So even if we had done the genetic analysis, and viruses would have been the same in both instances, we couldn’t have said it’s the first infection persisting.”Dr Pratik Patil
But is the presence or absence of antibodies the lone marker for immunity?
Dr Patil says that while there are other aspects as well, the presence of antibodies is the only measurable immune response we have right now. There are no tests available easily for the T-cell mediated immune responses. “This is all we can measure. Based on what we know, it’s highly possible this is a case of reinfection.”
Moreover, in the case in Hong Kong, the second bout of infection was found to be asymptomatic, indicating that the immune response may have been at play after the first time the virus truck the man. In the Bengaluru case, the woman showed mild symptoms both times.
So how would the virus culture test for the second infection help now?
He explains that it would help dismiss the chances of lingering infection. “The virus is not known to stay alive for this long. So if the virus culture is positive this time, it would boost the fact that this is a second infection.”
“In fact, the CT value, which was very low in the first case, was found to be even lower after nearly 52 days, again making it very very unlikely that the first infection had persisted.”Dr Pratik Patil
FIT had explained the concept of CT value in detail in a previous explainer. It is a type of virus concentration. The higher the concentration, the lesser are the number of cycles needed for the virus can be detected.
“Therefore, with the caveat that we don’t have the first sample to analyse, we feel that reinfection is a strong clinical possibility.”Dr Pratik Patil
Through this case, Dr Patil says, the importance of storing samples for longer durations also gets highlighted. “As per my knowledge, the ICMR has not come up with any guidelines for the labs on for how long they should store the sample. In Hong Kong and the US, they could do the genome sequencing after a few months as well, because they may have been storing the first samples. If our labs had stored it in this case, we could have tried to show if it was the same virus or a different one.”
“More importantly, we shouldn’t neglect or disregard the chances of reinfection. It is important to let everybody know that they shouldn’t let their guard down because they have been infected once,” he says.
Considering the millions of people infected around the world and only a few such proven cases, the situation may not be that alarming.
“There’s been more than 24 million cases reported to date,” Maria Van Kerkhove, a coronavirus expert at the World Health Organization, said at a briefing when asked about the Hong Kong report. “And we need to look at something like this at a population level.”
“From what we know so far, the chances are very very low. But it is important to continue to keep following the protective measures.”Dr Pratik Patil
(With inputs from The News Minute)
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