Health

Shutdown alone is not enough to break the chain, says epidemiologist Giridhara Babu

Mitigation and containment need to go hand-in-hand, says Professor Giridhara Babu, head of Lifecourse Epidemiology at the Public Health Foundation of India

In an unprecedented measure, India on March 25 began a country-wide shutdown for 21 days to cut the transmission chain of the novel coronavirus SARS-CoV-2. Till Wednesday, India had adopted the containment measures of screening, testing, isolating and tracing contacts. By shutting down, India has also adopted mitigation measures to break the spread.

At a press briefing on March 25, World Health Organization Director-General Tedros Adhanom Ghebreyesus said: “Shutting down population movement is buying time and reducing the pressure on health systems. But on their own, these measures will not extinguish the epidemic. The point of these actions is to enable the more precise and targeted measures that are needed to stop transmission and save lives.” Among the six steps that every country should take, the WHO chief said the production, capacity and availability of testing has to be ramped up and a system to “find every suspected case at community level” has to be implemented. The six measures are the “best way to suppress and stop transmission, so that when restrictions are lifted, the virus doesn’t resurge,” he added.

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Professor Giridhara Babu, Head of Lifecourse Epidemiology at the Public Health Foundation of India, Bengaluru, in an email to The Hindu’s R. Prasad, explains how the shutdown along with testing can help flatten the curve.

Prime Minister Narendra Modi said 21 days of lockdown will help cut the transmission chain. Is that true?

Yes, it is the bare minimum period we require to be sure. Prime Minister Narendra Modi’s call for a 21-day nationwide shutdown is an effort to break the chain of transmission. India’s COVID-19 fight could make or break the global war. The “incubation period” means the time between catching the virus and beginning to have symptoms of the disease. Most estimates of the incubation period for COVID-19 range from 1-14 days.

A lockdown for 21 days would be a great social experiment which allows social distancing. If followed strictly, it will contribute to delayed peak and to an extent, in flattening of the curve. Lockdowns may have to get extended in the areas with high transmission. It is important to identify such areas.

India has imposed the lockdown much earlier than many countries, including China, which failed to contain the initial spread of the virus. Although started late, the Wuhan shutdown slowed the dispersal of infection to other cities by an estimated 2.91 days, delaying epidemic growth elsewhere in China. Other cities that implemented control measures pre-emptively reported 33.3% fewer cases in the first week of their outbreaks compared with cities that started control later. The most effective interventions were suspending intra-city public transport, closing entertainment venues and banning public gatherings.

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Why then were Wuhan and many other cities under lockdown for two months?

In Wuhan, the measures started much later compared to what India is doing. It takes that much longer when you start late. The initial outbreak of COVID-19 started in China while it was spreading across before diagnoses and establishing preventive measures. Not just China, they had by then sent the virus to other countries as well.

As a result, longer lockdowns of nearly two months were required in some regions. Before the interventions, scientists estimated that each infected person passed on the coronavirus to more than two others, giving it the potential to spread rapidly. But between January 16 and 30, a period that included the first seven days of the lockdown, the virus reproduction decreased from 2.35 to 1.05. The number of new daily infections in China seems to have peaked on January 25 just two days after Wuhan was locked down.

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As of 16 March, roughly 81,000 cases have been reported in China, according to the WHO. Epidemiologists say that measures implemented during this time did work. Epidemiologists say China’s mammoth response had one glaring flaw: it started too late. In the initial weeks of the outbreak in December and January, Wuhan authorities were slow to report cases of the so-called mysterious infection. This delayed measures to contain it.

In China, implementing the measures three weeks earlier, from the beginning of January, would have cut the number of infections to 5% of the total.

How long does the virus persist in a person from the time of infection — whether asymptotic or symptomatic? Is it less than 21 days?

This is still under investigation on the dynamics of how the disease spreads from person to person. It is too early to provide conclusive evidence regarding this. Like SARS, emerging evidence shows that SARS-CoV-2 RNA can be detected in stool samples. A study has found extended duration of viral shedding can occur in faeces for nearly five weeks after respiratory samples turn negative for SARS-CoV-2.

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Will complete shutdown for 21 days alone be enough to break the chain? Is it right to say that shutdown only buys time?

It is right to say that shutdown not only buys time but also decreases the overall burden and delays the outbreaks in most places. Stronger containment measures done together with these mitigation measures will ensure in the flattening of the epidemic.

Mitigation measures or shutdown alone are not enough to break the chain of emerging COVID-19 pandemic. The containment strategies include identifying all cases which are positive and identify their contacts too. Once identified, cases will have to be isolated, and contacts will have to under quarantine.

Mitigation is a precursory measure and if containment is also not done, it is not going to help. Both need to go hand-in-hand.

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Also, reviewing of States where any single case is confirmed is the need of the hour. Contact tracing of all those people who might have been infected is highly needed. Only then will India succeed in current strategies to combat COVID-19.

Can aggressive testing alone cut the transmission chain?

Aggressive testing alone without mitigation doesn’t help in breaking the chain of transmission. Without mitigation, the spread of the infection from one person to another will happen at a faster rate. We may find a certain number of cases getting doubled every week, also the number of deaths. The lockdown is an opportunity for us to rapidly scale up the capacity to have enough resources to manage, isolate and provide intensive care for those who needed it. Both measures going hand-in-hand could have a reasonable effect on flattening the epidemic curve.

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The revisions in testing strategy involving accredited private laboratories too could not solve the issue since the only a particular number of potentially infected persons can be tested in a day. With the second highest populated country testing, everybody at a specific time is out of question. Therefore, we need to follow mitigation measures. I recommend the syndromic approach now, wherein we need to manage every case of fever, cough and respiratory distress as COVID-19 unless otherwise proved. Once testing is scaled up, this can get better.

Since no community testing was done, will the lockdown increase the risk for household contacts getting infected from an index case who not been tested?

Yes, there is a higher risk for people spreading the disease within the household if they are sick. Mr. Modi had asked people to stay wherever they are during the lockdown. This implies that even getting back to family at this period can put the person as well as the family at risk because anybody might be carrying the virus.

Even when living together, it is advised that people maintain physical distance. In case of suspicion, it is advised that people do not sleep in the same bed, not to hug or kiss each other, not to share any ordinary toothbrushes or towels and not to have sexual relationships. It is advised to maintain good hand hygiene and cough etiquette. Surfaces should be cleaned frequently. It has to be decided on how to share space when people are living with others.

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Should India find all suspected cases in the community and test them, as per WHO’s recommendation?

This virus effectively hides and quickly doubles. By testing only possible cases, we might miss many of those who are asymptomatic during screening. The best strategy is to test among the SARI (severely affected respiratory infections) admitted in the hospitals and the OPDs (out patient departments) of these areas. Many States have not even begun testing such cases. This is part of March 23 national recommendations. Therefore, strong national and local surveillance review is needed. There is a potential to cause illness suddenly in large numbers of people. Without having an idea of the total number of cases, it would become guesswork to plan for the future management of COVID-19.

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In the absence of testing suspected cases in the community, will transmission begin once the shutdown is lifted?

Yes, of course, if we do not implement containment measures effectively now. Ineffective implementation of physical distancing can further complicate the matter. The infected person will recover from mild cases at home or seek medical care for severe cases during the first few weeks of the strict lockdown period. During the later few weeks, newly infected family members will seek medical care or isolation, which will prevent further spread. Thus, the cases will decrease sharply by the end of the lockdown. Isolating all the people who are sick and their closed contacts is more critical as we are missing many now.

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Printable version | Mar 28, 2020 5:54:54 PM | https://www.thehindu.com/sci-tech/health/shutdown-alone-is-not-enough-to-break-the-chain-says-epidemiologist-giridhara-babu/article31173750.ece

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