Sealing areas with higher Covid-19 cases or 2-day work week with lockdown can contain virus, shorten epidemic duration: Analysis

As the Centre and states discuss strategies to reopen the economy as the deadline of May 17 nears for lockdown 3.0, a two-member team of professors at the Chennai

As the Centre and states discuss strategies to reopen the economy as the deadline of May 17 nears for lockdown 3.0, a two-member team of professors at the Chennai Mathematical Institute and Indian Institute of Science (IISc), Bengaluru, have drawn up a mathematical analysis that suggests sealing areas with high number of infected individuals or introducing a two-day work week with a lockdown can suppress the transmission of the virus that causes Covid-10 and shorten the duration of the epidemic. Both these measures combined with “tracing contacts and their contacts and sealing” (TC2S) reduces the virus’ attack rate by more than 30% compared to the current contact tracing approach.

HT Image

With Bengaluru as the study area, V Vinay, co-author and co-founder of tech start-up Ati Motors, with Chiranjib Bhattacharyya, a professor at the department of computer science and automaton, IISc, performed simulations of different post-lockdown strategies on the multi-lattice small world mathematical model.

“Lockdowns, though an effective policy for containment, imposes a heavy cost on the economy as it enforces extreme social distancing measures on the whole population. Unemployment is an inevitable outcome of economic downturn and lockdowns have resulted in significant job losses,” said Vinay. “There is now a growing view among scientists and many world leaders that rapid suppression of Covid-19 transmission must be the way forward. Our study provides alternatives to lockdown which are either more targeted or allows partial opening of the economy,” he said.

TC2S is a two-tier strategy that not only involves identifying and testing all individuals who came in contact with a patient — as is the current method — but also tracing their contacts, which would subsequently result in targeting asymptomatic individuals.

Similarly, a two-day work week (with stringent lockdown for remaining five days) is likely to result in 1,345 deaths per million with the epidemic lasting for 675 days. But this measure when coupled with TC2S leads to a drastic decrease of 34 deaths per million and the epidemic ending in 107 days.

The most preferred strategy, according to the paper, is hotspot surveillance, which not only lowers attack rates, but is also much faster in destroying the virus. If ward level sealing and opening (WSO) is introduced early enough, it is possible that the pandemic can be suppressed in the early stages in less time than currently-practiced lockdowns.

For instance, the model’s estimate on the duration of the epidemic is 115 days with 51 deaths per million during a lockdown. However, WSO along with TC2S results in a decline both in the length of the epidemic to 65 days with a death toll of 18 individuals per million.

The researchers said while WSO opens the economy much more than the two-day week policy, investment in testing could prove to be a challenge, especially in densely-populated urban wards in metropolitan cities. “The success of WSO policy crucially depends on the ability to test all residents in the hotspots... If there is substantial shortage of testing kits making WSO unviable then one can consider the alternative policy of opening the economy for two days a week. For both the interventions require contact tracing,” the paper reads.

Pointing out the lack of resources needed to implement TC2S that makes WSO more effective, Dr Lancelot Pinto, pulmonologist at PD Hinduja Hospital said WSO appears more feasible as compared to the two-day week alternative. Dr Pinto was not involved in the study.

“The success of WSO also depends on limiting movements across wards, and this might be labour intensive and difficult to implement (as opposed to movement between cities/districts). Reports from the zoning exercises so far suggest that the red zones are also the ones contributing disproportionately more to economic activity, and I’m not sure the model accounts for this,” said Dr Pinto.

On the alternative of the two-day work week, Dr Pinto said, “Our limited experience (with alcohol shops, for example) suggests that limiting access to a few hours a day (or a few days a week) is likely to lead to overcrowding during the periods in which economic activities are opened up, and will therefore be counterproductive. The model will have to take this into account.”

“Suppress, and not just flatten: Strategies for Rapid Suppression of COVID19 transmission in Small World Communities” was uploaded last week on medRxiv, a preprint server for health sciences operated by US-based Cold Spring Harbor Laboratory. The paper has also been sent to office of the principal scientific advisor to the government of India, K VijayRaghavan.

The authors have stated their conclusions are about the relative effectiveness of various strategies and not about absolute predictability. The study has also not considered issues related to civil liberties, and economic hardships of the proposed interventions.