A study of the dynamics of the second wave of the Covid epidemic, specifically for each state and district, shows that the onset, progression, peak and decline vary from district to district in each State. There are three parameters pertaining to the epidemic, each with its own wave and peak, namely epidemic momentum (rate of change in new cases based on a 7-day rolling average), documented daily numbers of new cases and cumulative numbers of active cases.
Typically, there is a consistent pattern of time sequence of these three peaks – momentum, new case numbers and active cases. Visualising the time of these peaks in a given district will enable health administrators to take appropriate action vis-a-vis the lockdown.
Lockdown is most effective in slowing down the epidemic momentum only on the ascending limb of the momentum graph. Well-timed lockdown provides time to prepare for surge capacity -- hospital beds, Intensive Care (ICU) beds, supply of oxygen and essential drugs. During this time, the focus should be on effective application of ‘social vaccine’ and to rapidly increase immunisation coverage – these will help reduce the rapid progression of the epidemic.
Social vaccine consists of Information-Education-Communication on Covid and Behaviour-modification Education for adopting all elements of Covid-appropriate behaviour -- mask-wearing, hand hygiene, physical distancing of arm’s length when all are masked, avoiding crowds and improving indoor ventilation during any activity.
Lockdown should be relaxed when the three peaks are over, as illustrated below. For the attention of administrators, there are two more parameters to study: mortality acceleration and numbers of daily deaths. When the graph of active cases peaks, the mortality acceleration would be in progress – we must expect a rapid increase in the number of very sick patients over the next 2-3 weeks -- administrators should be ready for enhancing healthcare surge capacity. Once the number of daily deaths also peaks
and declines, everyone can relax, lockdown can be eased gradually and carefully but the tempo of Covid immunisation and adherence to Covid-appropriate behaviour should be sustained.
Once the numerical mortality peak is over, the district will have surplus supply of essential necessities of hospitals, especially medicines and oxygen concentrators -- they should be shared with needy neighbours.In Karnataka, now all the peaks are over in most districts. Bengaluru Urban (see graph) is a typical example where all the peaks are over and mortality (not shown) has also started coming down. Careful relaxation of curbs can be introduced, maintaining ‘social vaccine’ and continuing immunization, in view of the slight apparent increase in infection momentum.
Even though the momentum of transmission is apparently increasing, it is still less than 0: since both daily numbers and active cases are declining steadily, this relative acceleration will not result in further rise of the current wave. Mysuru (see graph), on the other hand, is an example of a district where momentum and numbers of cases have peaked, but active cases are hovering high, likely to peak soon. We know that mortality is still on the increase. Therefore, it is not yet time to relax lockdown restrictions.As of this writing (16 June) in Chitradurga and Davanagere active cases are nearing the peak. These districts, along with Mysuru, need to urgently enhance hospital surge capacity.
In all the remaining districts of Karnataka, all three peaks are over; in addition, even mortality acceleration and numerical mortality peak are over and they can expect hospital admissions to progressively come down. They can begin allowing hospitals to admit non-Covid patients for elective treatment and surgery. They should, however, continue to focus on social vaccine and increase immunisation coverage.
(M S Seshadri is former Professor of Medicine and Clinical Endocrinology, Christian Medical College, Vellore, and currently Medical Director, Thirumalai Mission Hospital, Ranipet; Muru Subramani is former CTO at GlobalScholar and Research Engineer at Microsoft Research, Redmond, and currently researcher, Bhaktivedanta Vidhyapitha Research Centre, Mumbai; T Jacob John is former Professor of Clinical Virology, Christian Medical College, Vellore)