It’s too early to detect lock down impact

As incubation period is 14 days, the cases emerging now are older and they have to be discounted

02/04/2020, JACOB KOSHY,NEW DELHI

Empty spaces: A deserted highway near the Akshardham temple in New Delhi on Wednesday. R.V. Moorthy R.V. Moorthy

The impact of the lockdown on arresting the spread of COVID-19 can be gauged only after two weeks, government and independent experts suggest.

On the evening of March 24, Prime Minister Narendra Modi announced a nationwide 21-day lockdown to arrest “community transmission” of the novel coronavirus, or SAR-CoV-2. Between March 24 and April 1, the number of COVID-19 positive cases has more than doubled — from 606 on March 25 to 1,637 on April 1. This, however, was slower — about half the rate of growth from the week before when only 151 cases were confirmed on March 18.

The growth in number of positive cases in India is slower than in many countries that are dealing with the worst of the pandemic. On March 8, the U.S. recorded 541 cases in two days, and the figure nearly doubled to 994 cases. In the last week, however, it has risen by 75%.

Indonesia, which as on March 31 had 1,528 cases and therefore roughly in the league of India, is also recording a similar growth rate. It had 686 cases on March 24 or a little fewer than half the cases from today. Though it has laws restricting movement, there is no lockdown.

Government experts and independent researchers concur that it is early to estimate the impact of the lockdown on slowing down the spread of the virus. “The incubation period of the virus is 14 days. Therefore, the cases we are seeing are older cases (from before March 24). So only once these old cases are discounted can we judge the impact of the lockdown. Whatever models and statisticians say, nobody can really predict the outcome of the epidemic,” Raman Gangakhedkar, Chief Scientist, Indian Council of Medical Research, and spokesperson for COVID-19 communication, said at a press briefing.

Sujatha Rao, former Secretary of the Health Ministry, tweeted on Tuesday: “Impact of lockdown can only be known after April 5. Today’s infections are of the situation two weeks ago.” However, both of these reflect the extreme outer limit of the incubation period — defined as the time taken to contract the virus and an infected person manifesting symptoms. The World Health Organization says incubation is commonly five days.

For more testing

Giridhar Babu, an epidemiologist and physician associated with the Public Health Foundation of India, said it would take a minimum of three weeks and a lockdown would be useful only with heightened testing, particularly to catch those who might be carrying the virus but were not yet manifesting symptoms. “Lockdown alone, without an increase in finding the new cases either through a syndromic approach or increased rate of testing, is not enough to break the chain. Also reviewing of the States with silent areas [where very few cases are reported] is important,” he said in an e-mail.