MADURAI: Indicating reinfection of Coronavirus, four healthcare workers at Government Rajaji Hospital (GRH) tested positive for Covid for the second time. While sources in the health department say there is no mechanism in Tamil Nadu to monitor instances of re-infection among the public, experts opine that re-infection is not a cause of worry as immunity developed against respiratory viral infections is generally short-lived.
Swab turns positive for 2nd time
According to GRH sources, four healthcare workers at the hospital -- two doctors and two nurses -- tested positive for COVID-19 for the second time. "Of the four healthcare workers, three were posted on regular Covid duty while one (a doctor) belongs to a non-Covid department. All four were infected with Coronavirus for the first time (tested positive during RT-PCR test) in June, July when the district witnessed a surge in caseload. With an interval of 45 days to two-and-a-half months since the first infection, the four staff tested positive for COVID-19 again during RT-PCR test in the last couple of months. Between the first and second infection, one of the two nurses had, in fact, tested negative for COVID-19 thrice, upon completion of Covid duty," they added.
All the four doctors and nurses were symptomatic during the first infection period and were asymptomatic and had high titre (concentration of) antibodies during re-infection, sources pointed. While the two doctors -- a postgraduate student and an assistant professor -- are aged 24 and 35, respectively, the two nurses are middle-aged, added a hospital official.
Is it re-infection?
Public health expert and former Director of Public Health and Preventive Medicine Dr K Kolandaswamy said, "Viral shedding takes place for a maximum of one month since the infection, after which the remnants of the virus can be considered gone completely from the body system. So, turning positive for Coronavirus after the one-month period of viral shedding can be termed as re-infection."
No data on re-infection in Tamil Nadu
When asked about the number of cases of re-infection reported in Tamil Nadu so far, sources in the health department said that no such data was available as there is no mechanism in the state to monitor re-infection of Coronavirus. "Collection of data on re-infection among the public is not a priority now since only one or two such cases are reported sparsely from very few places. Further, it is a tedious process as most people would not be willing to divulge their Covid history. Such instances are promptly reported only by healthcare professionals who undergo covid tests routinely," said a senior epidemiologist. He cited repeated exposure as a reason for re-infection among healthcare workers.
Meanwhile, the Director of Public Health and Preventive Medicine Dr T S Selvavinayagam said Tamil Nadu has not recorded any case of re-infection officially and that re-infection claims were subject to careful study, if formally notified from districts concerned.
Fear not, experts say
However, experts opine that re-infection of vivid should not be a cause of concern since the immunity developed against most respiratory tract infections is short-lived.
Noted virologist Dr T Jacob John said the immunity developed against most respiratory viral infections are short-lived or incomplete, thus leading to re-infection - a common phenomenon. "In case of these infections, the immunity does not prevent re-infection but prevents onset of diseases during re-infection. Re-infection is not a serious concern in Covid treatment or vaccine development. But, in a scientific outlook, a study on re-infection is necessary to learn about the pandemic in all angles," he pointed.
Dr Kolandaswamy told, "From public health point of view, a cause of concern over re-infection does not arise as it won't create any impact in managing or controlling the pandemic. Due to insignificant number of such instances, re-infection does not change the disease dynamics. It can be studied only for academic and research purposes."
Recording viral strain
GRH Dean Dr J Sangumani said that few samples of extracted Coronavirus RNA of patients infected for the first and second time have been sent to the King Institute of Preventive Medicine, Chennai for the purpose of recording the viral strain for future reference. Results are awaited, he added.