Thread by @agrawalmanindra

Starting a new thread on analysis of lockdown in various states. First, let us examine UP. The plot for UP and SUTRA projections for it from 1st March are below.

UP went through two phase changes in this period. First started on 15th March with 10 days of drift. In this phase, the contact rate went up to 0.53 (95% CI: +- 0.03) from 0.4. And reach roughly doubled. This double whammy caused sharp rise in infections as is evident.

Next phase change started on 21st April with 12 days of drift. In this phase, contact rate went down to 0.28 (95% CI: +- 0.01) and reach further increased by more than 50%.

The increase in reach corresponds to expansion of pandemic in rural areas. The decrease in contact rate is due to lockdown, with people also becoming more careful. The reduction in contact rate more than made up for increase in reach and so cases started reducing although slowly.

What if the lockdown was not there? We plot two alternative scenarios. Red curve is for contact rate not changing at all, and green for contact rate reducing to 0.4. Peak value is approx 70K in former and 50K in latter.

So lockdown came at the right time! BTW, the lockdown in UP is not very strict: many activities are permitted, including people moving from one place to another as long as crowding does not happen. It appears to be a very successful strategy.

Continuation of lockdown beyond 23rd may not be beneficial unless there is possibility of pandemic to significantly expand its reach. We cannot predict how much more can reach increase in absence of calibration by a sero-survey. Those with ground-level knowledge should decide.

Second state to be analyzed is Delhi. The actual plot and SUTRA projection is below.

Delhi also had two phase changes since March. First started on 27th March with 9 days of drift. The contact rate went down from 0.59 to 0.47 (95% CI: +- 0.01). Reach almost doubled. High contact rate along with big rise in reach resulted in sharp rise in infections.

Next phase started on 22nd April with drift period of 3 days. Contact rate came further down to 0.34 (95% CI: +- 0.01). Reach hardly changed. This reduction, due to lockdown, held back rise of infections.

The red curve shows the trajectory with contact rate 0.47. Those following my tweets on states would recall that I was showing red curve as trajectory and wondering why is actual curve bending much earlier.

The red curve peaks at around 37K. So lockdown achieved significant reduction in cases, though not as dramatic as UP.

Going forward, it appears that reach may not increase much further, and so continuing lockdown may not be very useful. Green curve shows trajectory if contact rate increases to 0.47 from 24th May.