The 30th reported case is considered for the baseline since the growth in cases since the first reported case/clutch of cases has seen widely varying timelines.
How successfully India is able to control the spread of COVID-19 in the country will depend on how effectively the states that have recorded the highest number of cases so far are able to flatten the transmission curve — that is, how well they are able to enforce social distancing and quarantining.
An analysis by researchers at the Institute of Mathematical Sciences shows that the 21-day lockdown may have helped flatten the curve of COVID-19 spread in India — the study talks of a slight but discernible flattening beginning April 6, possibly because the 21-day lockdown resulted in lowering of contact between people.
But, the trend of the spread of the disease from Maharahstra, Delhi and Kerala show that a flattening of the curve could be still some distance away. Considering the day of the reporting of the 30th case as day-1, and mapping for how the disease has spread since shows that out of these states, only Kerala has managed to stabilise spread while Maharashtra and Delhi, as also India, see the spread curve trending upwards. The 30th reported case is considered for the baseline since the growth in cases since the first reported case/clutch of cases has seen widely varying timelines. For instance, while Kerala recorded its first three cases on January 31, it reported a spike in positive cases only around mid-March; on the other hand, Maharashtra recorded two cases on March 9, and by March 15, it had reported 32 cases.
Delhi’s reported cases doubled from 30 in just 6-7 days, and Maharashtra, too, roughly took the same time. While the accompanying graphic shows how the spread has trended since the 30th infection, only Kerala (of the three states considered here) shows a flattening. Reading the reporting of cases, and consequently, the trends of rise for the states must factor in the difference in testing levels, the demographic details of the infected, initiation of local social distancing measures, etc, apart from factors like the steep rise in reporting after the Tablighi Jamaat spread got uncovered.