Chennai: Chennai cannot afford to let its guards down now that fresh coronavirus cases have been brought under check because the curves of other metropolises that showed similar dips have started displaying an upward trend, say researchers studying mathematical models on the viral spread and administrators batting the disease on the frontline.
Sitabhra Sinha, senior researcher and professor at the Indian Institute of Mathematical Sciences, says an example to support this word of caution is the city of Mumbai. The Maximum City had an R Value less than 1 during July1 and 8, but the metric has gone above 1 now. The R Value is the parameter determining the viral spread in a community. R refers to the effective reproduction number which changes with time as more and more of the population exits from the susceptible category as a result of infection, and subsequent recovery or death.
Sinha says Kolkata, too, had an R Value less than 1 during June 19 and 29 but it has risen to 1.31, give or take 0.01, for the period of July 1-18. The highest in the group is Bengaluru at 1.41 for July 3-18, a city that had originally won praise for its containment of the disease.
In the same breath, Sinha says there were a multitude of factors contributing to the change in R Values, making it a difficult metric to get to the bottom of. “It is difficult to predict how R will change in the future. Given R one can estimate the active case numbers in the near future, but R itself depends on so many unknown factors that it is difficult to predict it.”
Chennai, among other major metros, has been bold in experimenting a lot with lockdowns. It brought back severe measures beginning June 19 and let them run until July 5, the effect of which is seen in the R Value recorded so far. However, with the metric rising again now: “Note that R has slowly started rising again even though it is still less than 1 (an exact number cannot be estimated for the last few days). If the relaxation that started from July 6 leads to another round of amplification of cases that will again drive R to values greater than 1, then we are likely to see it this week (as we will complete 2 weeks following the lockdown relaxation).”
The apprehensions spelt out by Sinha are echoed by various health department officials of Tamil Nadu, although some of them could be a little early in claiming that relaxations have not fanned fresh cases. The state health secretary J Radhakrishnan had initially warned that physical distancing, masks and washing hands frequently are the only vanguards against the virus. In Chennai, the coronavirus had gripped the northern regions characterised by working class inhabitants but the scenario has changed now. North Chennai has largely brought it under control but areas such as Anna Nagar and Kodambakkam, which boast pockets of very posh localities, have proved to be inefficient in fighting the virus.
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