With and without social distancing, how many people can a COVID-19 patient infect?

'R0' or R naught is a mathematical term that indicates the contagiousness of a virus, its basic reproductive number. An R0 above 1 meant the patient will, on an average, infect more than one other. Referring to an ICMR study, Union health ministry Joint Secretary Lav Agarwal said the current R0 for the coronavirus infection is somewhere between 1.5 and 4. Highlighting the significance of social distancing measures, he said, "If we take the 'R0' to be 2.5 then one positive person can infect 406 people in 30 days, if the lockdown and social distancing measures are not in place, but if social exposure is reduced by 75 per cent then that one sick person will only be able to infect only 2.5 persons," Agarwal said.

Social distancing, according to the study, is mathematically the most effective way to flatten the curve. Take a look at this statistic: The ICMR study has found that a COVID-19 patient can infect 406 people in 30 days if preventive measures such as lockdown and social distancing are not implemented. With preventive measures in place, the possibility of the infection can be reduced to an average of just two-and-a-half persons per patient in the same period, Agarwal said.

He appealed to the people to adopt social distancing and follow the lockdown order, saying this is a very important intervention in terms of coronavirus management.  "Hence, again request you to follow social distancing, it is social vaccine in management of COVID-19," he said.

According to NDTV, India registered 508 new coronavirus cases in the last 24 hours, taking the total to 4,789 while the number of deaths rose to 124 with 13 new ones. Now, the Centre has to, by the end of the week, take a decision as to whether the lockdown is to be extended. Reportedly, many states have asked that the lockdown be extended. Prime Minister Narendra Modi had also indicated towards a graded approach to lift the lockdown.

With the number of cases of COVID-19 shooting up across the country, the Centre had adopted a policy of "cluster control" along with social distancing measures to hold the pandemic. The cluster containment strategy would "include geographic quarantine, social distancing measures, enhanced active surveillance, testing all suspected cases, isolation of cases, quarantine of contacts and risk communication to create awareness among public on preventive public health measures", the document stated. As far as the evidence for implementing geographic quarantine is concerned, the document cited the H1N1 Influenza Pandemic. "This suggests that while the spread of COVID-19 in our population could be high, it's unlikely that it will be uniformly affecting all parts of the country," the ministry said while stressing this calls for differential approach to different regions of the country, while mounting a strong containment effort in hot spots.

Large-scale measures to contain COVID-19 over large territories have been tried in China. Mathematical modelling studies have suggested that containment might be possible especially when other public health interventions are combined with an effective social distancing strategy, the document stated. The authorities will do extensive contact tracing and active search for cases in containment zone, test all suspect cases and high risk contacts, isolate all suspect or confirmed cases, implement social distancing measures and intensive risk communication as part of the cluster containment strategy.

For large outbreaks amenable to containment, the documents stated that the strategy will remain the same but vary in extent depending upon spread and response to be mounted to contain it. It will also include implementation of social distancing measures, with strict perimeter control, providing chemoprophylaxis with hydroxychloroquine to all asymptomatic healthcare workers and asymptomatic household contacts of laboratory confirmed cases and further intensification of risk communication through audio, social and visual media.