E-Paper
Effective testing reduces cases, key to successful lockdown exit, finds study
The study found that a single lockdown with no testing merely delayed the peak number of infections without affecting the quantum, but effective testing and lockdown reduced the peak infection by roughly 80%.
A periodic lockdown, combined with extensive testing, may be the best strategy to stop the spread of the coronavirus disease (Covid-19), a new modelling study has found, indicating that non-pharmaceutical interventions are significantly less effective in the absence of ramped-up screening and strict quarantine.
The working paper, published by a group of 10 scientists from Chennai, Bengaluru, Goa and Pune, looks at three kinds of lockdowns: a 30-day single lockdown (India’s ongoing lockdown is to continue for 40 days); a periodic lockdown of seven days followed by five days of relaxations; and a light-switch lockdown, in which restrictions are clamped for two weeks every time the number of infections cross a particular threshold.
The study found that a single lockdown with no testing merely delayed the peak number of infections without affecting the quantum, but effective testing and lockdown reduced the peak infection by roughly 80%.
A periodic lockdown with no testing reduced the peak by roughly 60% while periodic lockdown, testing and quarantine reduced it by about 90%. A light-switch lockdown reduced the peak further – because restrictions came into effect every time a threshold was crossed – but the disease was seen to persist in the community. “In this case, the number of infected cases will just keep oscillating between some minimum value and the threshold. Thus, the disease will persist as those susceptible keep getting infected,” said Snehal Shekatkar, a professor at the Centre for Modelling and Simulation, Savitribai Phule Pune University, and one of the authors.
In all three scenarios, the efficiency of lockdowns was significantly increased by ramping up testing.
Scientists found while the light-switch model was the best theoretically, it was not of much use practically because the total number of infected individuals is never known, and, therefore, preferred the periodic lockdown model.
A second simulation also showed that for periodic lockdown model, different combinations of lockdown days and workdays were possible to achieve similar number of hospitalizations and infections. For example, seven days of lockdown corresponded to five work days but 20 days of lockdown allowed 10 work days – for the same number of cases.
The study, which did not take into account the economic and social costs of a lockdown, also offered two clues about exiting lockdowns.
The first was increased testing. “Lockdown substantially slows down the spread, but doesn’t get rid of the virus. If enough tests are not done, infected individuals will start infecting the healthy ones when the lockdown is lifted. Thus, massive testing during the lockdown is the key to locating these infected cases so that the lockdown doesn’t need to be extended,” said Shekatkar.
The second was on exercising caution while opening transportation networks. Considering 318 cities connected via direct rail links, the scientists found that in the absence of any testing and quarantine, it took between 60 and 90 days for an infection to start in a node (Delhi or Mumbai) and sweep across the country.
“We tried to show that starting transportation has a potential risk until the entire population is cured. Of course, our model does not incorporate economic costs and policymakers can consider alternatives such as starting local transport and limiting the number of people,” said Bhalchandra Pujari, another author.
“But ramping up tests or keeping testing facilities along transportation routes may be a feasible solution,” he added. The 10 authors of the paper are part of the 500 scientists’ consortium, Indian Scientists’ Response to Covid-19.
