Ahmedabad Municipal Corporation (AMC) has reported four cases of Covid-19 reinfection between August 18 and September 6, nearly four months after they tested positive for the first time.
The four who tested positive again are two male resident doctors aged 33 years from the Gujarat Cancer and Research Institute (GCRI) and LG Hospital, a 26-year-old woman resident doctor from LG Hospital and a 60-year-old homemaker from Behrampura. They had first tested positive between April 13 and April 21. All had subsequently recovered and were discharged after testing negative through RTPCR tests at the time.
The resident doctor and the homemaker were also part of the recent seroprevalence survey conducted in AMC jurisdiction that found an absence of antibodies in 40 per cent cases of the 1,816 known confirmed cases’ samples which were studied. The 60-year-old was among the 60 per cent in whom antibodies were found and the resident doctor was in the 40 per cent in whom no antibodies were found.
A press release from AMC said that among the four patients who tested positive again, “one has history of visit to Kerala just before the second infection whereas the other three were in Ahmedabad.”
On Monday, the 60-year-old woman, who was admitted at Ratan Hospital under the AMC bed quota, was discharged. Among the three resident doctors, one is undergoing treatment at GCRI and is stable and the other two are in home isolation, according to AMC.
The genesis of the said “reinfection” in the four remain inconclusive and according to an AMC health official, while the three resident doctors may have been infected at the hospital, the source remains unknown in the case of the 60-year-old who was also incidentally the first case of ‘reinfection’ in Ahmedabad.
The release stated that the re-surfacing of the virus in cured patients was, “very much in line with AMC sero-prevalence survey.”
The AMC’s study concluded that the 40 per cent of cases who tested positive, lost antibodies and theoretically this meant that they are susceptible to new infection.
However Dr Atul Patel, infectious diseases specialist and part of the medical experts’ panel of the state government, is circumspect of the AMC serosurvey study and its findings, with respect to the absence of antibodies in 40 per cent of the confirmed positive patients and advises caution “before claiming loss of antibodies from previously antibody positive subjects.”
“We need to go for verification with better antibody testing because a number of the rapid antibody kits have shown a low sensitivity (for detecting antibodies)… There are so many intricacies involved in determining the presence of antibodies…Antibody testing should include measurement of total antibodies as well as the IgG antibody…,” said Dr Patel.
According to AMC, all four had mild to moderate symptoms the first time, and four months later, the three resident doctors’ samples reflect an absence of antibodies while the 60-year-old on the other hand has antibodies.
Globally, there were instances of purported reinfection declarations which were eventually found to have been instances of prolonged and intermittent shedding of the virus or its genetic material. However, AMC said these four are being considered as the statistically rare cases of reinfection, since two of them had coincidentally been included in the two serosurveys of AMC, and thus they have some evidence to track the trajectory of the supposed cases of reinfection.
Dr Patel, however, said this is a “premature” conclusion to draw. “In Gujarat, we do not have the capacity to differentiate between prolonged viral shedding versus reinfection. An RTPCR test cannot differentiate if what it is detecting is an actively replicating virus or a dead viral particle or fragmented viral particle. The best method to determine it would be to go for viral culture, available at the National Institute of Virology (NIV), Pune, which will determine if the said virus is actively replicating,” said Dr Patel.
Dr Patel also pointed out that there have been instances where patients have continued to test positive for a month, and cited the case of a Bhuj patient who tested positive for more than two months, thus establishing the case for prolonged viral shedding.
An AMC official said, “A drawback we are facing at the moment is there was no policy in place that permitted storing of the samples of whosoever tested positive. We don’t have previous samples to compare with for the patients reinfected,” and hoped for “a policy change” now with the reporting of these cases to the WHO and ICMR.
Dr Patel also mentioned a second scenario. Covid-19 has led to an increased number of patients developing multiple system inflammatory syndrome where the Covid-19 symptoms are mimicked. He explained that while such cases would ideally test negative for Covid-19, there may be cases where dead or fragmented viral particles continue to exist in the system, leading to a Covid-19 positive test, thus leading to the diagnosis that the patient has Covid-19.
While blood and nasopharyngeal samples of the cases have been sent to Gujarat Biotechnology Research Centre (GBRC) in Gandhinagar for genome sequencing and further analysis of virus genetics, according to a an AMC press release, when The Indian Express reached out to GBRC director Dr Chaitanya Joshi, he said, “We don’t have proper samples to analyse reinfection, so I can’t comment on it.”
Dr Patel added, genome sequencing as well cannot determine if a said case is that of prolonged viral shedding or reinfection.
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