One of the first peer-reviewed studies on the impact of physical distancing on the spread of Covid-19 has used mathematical modelling to conclude that the measures delay the spread of the virus, defer and diminish peak infections, and shrink the total number of cases, but removing them too soon could lead to a second wave of infections.
The results of the projections based on Wuhan, the Chinese city that was the epicentre of Covid-19, were published in the scientific journal Lancet on March 25. Wuhan imposed nine weeks of complete self-isolation starting January 23, which gradually reduced new infections to zero by March 18. Since March 23, restrictions have been eased, allowing people to leave their apartments in a phased manner.
Based on data from Wuhan, mathematical modelling showed that physical distancing reduced the projected median number of infections in mid-2020 by more than 92% and for end-2020 by 24%, said the study. This means that 92% fewer cases would be seen by mid-2020 and 24% fewer by end-2020 than if the curbs had not been imposed.
The study recommended keeping the curbs in Wuhan in place until April, instead of beginning to relax them as is being done, and then allow a staggered return to work with only 25% of employees returning in the first two weeks. It suggested that 100% of the workforce return to work and schools be reopened only four weeks after the curbs are relaxed. This, it said, would flatten the second wave of infections and prevent healthcare systems from being overwhelmed with increased patient load.
The Chinese response in Wuhan is being watched keenly by the 181 countries currently battling the pandemic.
Between March 25 and April 7, India’s cases went up from 606 to 3,577, according to Coronavirus Monitor, a HealthCheck database. The country has so far reported 114 deaths.
“The key takeaways from this [study] to me are that social [physical] distancing interventions work,” said Gagandeep Kang, executive director of the Translational Health Science and Technology Institute and one of India’s leading clinician-scientists. “It tells us that if you remove the social [physical] distancing that you have for travel and you reopen schools, then you are at risk of a bounceback in cases.”
Researchers from the Centre for Mathematical Modelling of Infectious Diseases at the London School of Hygiene and Tropical Medicine who carried out the modelling acknowledged that the results would vary based on the extent and duration of the measures taken, so Wuhan’s experience could not be replicated exactly elsewhere.
The role of children in spreading the infection is currently not well understood, and the researchers said this uncertainty could change the projections. In nine out of 10 cases where children are infected, the symptoms have been mild, as IndiaSpend reported on March 30, but children could pass on the infections to the more vulnerable in the family, such as the elderly.
Worsens cluster spread
Physical distancing would buy health systems more time to expand and beef up to respond rather than be overwhelmed when the number of cases begins to grow, the study suggested. Recent experience in Italy and the United States – both countries with advanced medical systems – has shown hospitals unable to cope with the sudden surge of patients, forcing healthcare professionals to make hard choices on whom to save.
India’s 21-day lockdown is aimed at curbing the spread of the virus but public health experts warn this could worsen transmission within households, especially in households where generations live together.
“If you limit the number of interactions [between people], then theoretically you will stop the spread of the virus,” said Claire Standley, assistant research professor at Georgetown University Center for Global Health Science and Security in the United States. “Some of the preliminary data from Wuhan showed that as the strict quarantine and lockdown policies came into place, household transmission was elevated.”
The Lancet study too found such clusters of infections within households in Wuhan but the study was not designed to look at household transmission in particular. In the Latin American country of Ecuador, where strict quarantine measures were imposed after the virus began to spread, the official death toll from Covid-19 was at 191 till April 7.
Cluster transmission though has led to deaths within households. Strict quarantine measures have reportedly prevented families from cremating the dead, with desperate members forced to abandon the decomposing bodies on the streets.
“Those [lockdown] measures are good at slowing and flattening the curve,” said Angela Rasmussen, a virologist at the Columbia University’s Mailman School of Public Health, who studies host responses to infection and has investigated multiple viruses that pose a public health threat. “That doesn’t necessarily mean it is going to reduce the total number of people who are going to be affected.”
India’s lockdown announcement on March 23, triggered large-scale migration of workers from metros to their villages across India, as IndiaSpend reported on March 28. The Lancet study has not accounted for the role of such migration in the spread of the epidemic.
The state of Chhattisgarh currently has only two functional Covid-19 testing centres, while Bihar and Odisha have four each. The migrants returning here are faced with healthcare systems that have no capacity to test them, with the result that India’s real Covid-19 figures would be far higher than the official reports, experts told us.
The only way out
The World Health Organisation director-general’s plea on March 16 to countries to ramp up testing must remain central to India’s Covid-19 strategy, experts said, as the country buys time with the lockdown. Indian states that are testing more patients are reporting higher Covid-19 cases, as IndiaSpend reported earlier.
For long, those tracking the disease have remarked at India’s mysteriously low Covid-19 figures. The growing number of cases only confirms what experts have pointed out for weeks now: India simply was not testing patients to know whether or not they had Covid-19.
India’s tests per million figure stands at 66 as opposed to 29,591 for Bahrain and 11,448 for Italy. The United States is conducting 5,027 tests per million people.
“Once you have the lockdown in place, there also need to do follow ups to identify new cases and to make sure that they are being treated appropriately,” said Standley of Georgetown University. This, she said, would also help understand how the transmission is changing over the course of time in the population.
What would Covid-19 spread after lockdown look like? Experts do not have an answer to this question, as the limited extent of testing and data allows little room for analysis. A paper by researchers at the University of Cambridge that is not yet peer-reviewed suggests that India will need two more lockdowns of 28 days and 18 days each, following the current 21-day lockdown, to end the pandemic. These lockdowns would be lifted for a few days in between to allow people to take care of any immediate needs and prepare for the next lockdown, the paper suggested.
It is also too early to conclude whether India’s lockdown has helped prevent contagion, experts said. “I don’t think we know enough...to say that this has made a difference because one week is when your cases start emerging, probably two if you were infected before the lockdown,” said Kang of Translational Health Science and Technology Institute. It will be another two weeks after the curbs are lifted before the results of the lockdown becomes clear.
“India and everywhere else, where lockdowns are in place, the success of that is going to be measured in how many patients are going into the healthcare systems and how overwhelmed those healthcare systems really get,” said Rasmussen of Mailman School of Public Health.
This article first appeared on IndiaSpend, a data-driven and public-interest journalism non-profit.
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