Can corona strike twice?

Once bitten, one is likely to have some immunity but how much and its duration is anybody's guess; no case of reinfection reported in state so far

Can you get coronavirus twice? Experts and doctors don't know for sure yet, but they believe it is unlikely. So far, more than four lakh people have won the battle against the SARS-CoV-2 virus in the state, but none of them have re-contracted the infection. Health experts think people who have had Covid-19 once will have some immunity against a repeat infection. But no one can tell how much protection and the duration for which the immunity will last.

However, members of the state taskforce and health officials said there was no evidence of patients being reinfected and it would be too early to comment on the subject. No such case has been reported in the state so far.

So far, 4.08 lakh Covid patients have recovered and been discharged across Maharashtra, of which 1.02 lakh are from Mumbai but no case of recurrence of the infection has been reported. Further, considering that the disease is eight to ten months old, it is too early to say whether a patient could be reinfected or not. It will be years before data on how long a recovered patient remains immune to reinfection.

“As of now, no evidence of reinfection has been validated, and theories on when antibodies in mild and asymptomatic patients disappear are pure guesswork. The few reported cases of reinfection from Korea and a couple of other countries were misrepresentations. They found traces of viral genetic material (RNA) in nasal swabs, which may be a remnant of natural infection before recovery. RNA doesn't cause disease or spread infection.

When the viral load is low and there's no transmission, it's of no epidemiological significance because the person doesn't get sick or infect others,” said one of the task-force members appointed by the government . Scientist Dr S Ranganathan said, “How long the virus would stay in the host with reference to the novel coronavirus is not known until now. So, if af ter two months a person were to show reinfection, it would be difficult to say whether the pre-existing virus became active or the person contracted it again. Normally, a second infection is uncommon if the infective agent is totally removed.”

Dr Lancelot Pinto, Consultant Pulmonologist, P D Hinduja Hospital & MRC, said Covid reinfections do seem to be a rare occurrence, but the fact that must be taken into account is that it has only been just over seven months since the initial infections began. “We know that antibodies against SARS-CoV-2 wane with time, but whether this waning makes individuals susceptible to re-infection, or whether cell-mediated pathways continue to protect despite falling antibody levels is not known. We have seen a few cases of re-infection, but at this time, they seem to be the exception and not the norm,” he said.

Health experts said there were many studies going on across the world, but reinfection with SARS-CoV-2 seems unlikely, taking into consideration knowledge on viral-neutralising antibody duration from past respiratory illnesses, the type of specimen collection and technical errors associated with each component of swab testing, the methods used before discharging these patients, the presence of fecal viral RNA without evidence of replication-competent virus in fecal swabs, and finally the reassurance from animal studies. “Till we have enough data to suggest that these patients are non-infective, we must maintain vigilance during the convalescence period also and must take into consideration the probability of genetic mutations as observed, rather than reinfection by the same strain,” he said.