Mumbai: As India approaches the May 3 deadline for lifting the nationwide lockdown , top epidemiologists are divided over the future course of Covid-19 management and the strategy to be followed in getting the country back to work.Two veteran infectious diseases experts — Jayaprakash Muliyal and T Jacob John, who were at the forefront of the leprosy eradication and pulse polio immunisation programmes, respectively — feel it’s time to end the lockdown, with one of them describing a long-term shutdown as akin to ‘burning the house to kill a rat’.Experts from the official health establishment, however, advocate phased relief, with strict containment measures guided by surveillance mechanisms. They warn that achieving ‘herd immunity’ is a costly proposition that will result in a surge of positive cases, which will overwhelm the healthcare system.“My advice is: Keep the elderly out of the picture for the time being, as the disease hurts them the most. So, we quarantine the old for two-three months and let the youngsters get to work,” Muliyal told ET.“Several of them will fall ill, unfortunately, but there will be adequate space in hospitals to treat them. So, mortality can be further reduced. And then, we reach the point of saturation, or herd immunity,” he added.Muliyal has been a big proponent of the ‘herd immunity’ concept. This is a strategy where you let natural immunisation take place by a large population contracting the disease, thereby halting the spread of the infection.This controversial concept was initially promoted by UK Prime Minister Boris Johnson, before the country reversed its stance on the issue. Recent random antibody testing in New York reveals that 20% of that city’s population may have contracted Covid-19 and recovered on its own.According to Muliyal, herd immunity may already be developing in India as reports come in of people with sub-clinical and mildly clinical symptoms. “Along with epidemic, the natural immunisation process is also going on… all I am saying is, don’t forget that,” he said, adding the country needs to worry about availability of beds in hospitals. This disease seems to spare the young, as mortality rates in that segment are very low, Muliyal said.John described the lockdown as an act of stopping time. “It just froze time. Once you unfreeze time, whatever you stopped day before the lockdown, it will pick up. So, lockdown is not simply for reducing the transmission or flattening the curve, it is because you need time to prepare. And if you didn’t prepare in two weeks, you won’t be prepared in four weeks either,” he told ET.John compared the lockdown effort for hunting the virus to the story of a ‘clever man’, who burnt down a house to kill a rat. “The lockdown was good for two weeks, three weeks was the upper limit. Anything more than that will be like burning the house down,” he said.However, physical distancing measures must continue, John said.At the other end of the spectrum, two experts who are part of the National Task Force of the Indian Council of Medical Research (ICMR), said the country needs to get used to a new normal.“The best post-lockdown strategy is to implement phased relief, with stricter containment measures guided by strong surveillance mechanisms. Herd immunity as a concept is mostly theoretical at this stage since reinfections are known to exist in communities that have had the infection earlier,” said Giridhara Babu, an infectious diseases expert with the Public Health Foundation of India “I think the lockdown has been successful in keeping the burden low, helping in preparedness and scaling up testing. It has proven most models predicting a worse scenario wrong,” said Sanjay Pujari, director of the Institute of Infectious Diseases.Pujari said herd immunity may be a good concept for infections with low morbidity and fatality rates. But in case of Covid-19, trying to achieve herd immunity will lead to a surge in cases which will overwhelm health systems.“Imagine the burden when 50-60% of the population (the number needed to achieve herd immunity) is infected. Research on immune response to SARS-CoV-2 is still evolving. It is better to achieve herd immunity by using a vaccine and in the meanwhile prevent getting infected with physical distancing, hand hygiene, cough etiquette and universal mask use,” Pujari told ET.