"Those who are asymptomatic or are in the presymptomatic stage will pass through screening mechanisms and may reach areas where there have been minimal or fewer cases," Guleria said.
He said there was a need for more intense surveillance and monitoring in areas where migrants have returned to contain the spread of the disease.
If proper social distancing and hand hygiene is not maintained at a time when people are out on roads, the coronavirus
infection will transmit much faster, he said.
Passengers at Terminal 3 of Delhi airport. Photo by Dalip Kumar
Guleria also noted that testing capacity has been significantly ramped up which is reflecting in the increasing number of cases being detected.
Commenting on the partial resumption of rail and road transport services and migrants returning to their native places, Dr Chandrakant S Pandav, former president of the Indian Public Health Association and Indian Association of Preventive and social medicine, said the floodgates have been opened.
"This is a classic case of creating an enabling environment for coronavirus
to spread like wildfire. In the coming few days, the number will rise dramatically. While it is true that lockdown
cannot go on forever, the opening up should have been in a measured, calibrated and informed manner," he said.
"Travelling leads to the spread of the infection. Now, the government will have to ensure even stronger surveillance to curb the infection but if that will be done is something to be observed," he said.
The death toll due to COVID-19 rose to 4,167 and the number of cases climbed to 1, 45,380 in the country, registering an increase of 146 deaths and 6,535 cases since Monday 8 am, according to the Union Health Ministry.
Dr K K Aggarwal, President of the Confederation of Medical Association of Asia and Oceania (CMAAO), and former IMA President said there will be a further surge in cases in the coming days if migration continues without any proper social distancing.
"Within the next ten days, the cases will cross two lakh. The very fact that the number of cases was rising before the end of the third lockdown
and continuing during the fourth lockdown
means that people are not following physical distancing as required," he said.
"Even in the last week of May when the temperature is very high, the rising number of cases would mean that human-to-human transmission is more important than surface-to-human transmission. Normally in heat the surface-to-human transmission should have reduced the new cases by half which has not happened," Aggarwal said.
However, Professor K Srinath Reddy, president of the Public Health Foundation of India, said an increase in the number of cases reflects both an increase in testing rates and an increase in spread.
"What we need to see is the number of new tests performed per day and the number of new cases that were identified from them. That gives a better idea of the rate of a spread than the total number of new cases alone.
"We also have to see if the testing criteria have remained the same between the two periods of comparison. We may open up gradually but will have to continue case detection, contact tracing, and follow personal protection measures as vigorously as possible," he added.
A total of 31,26,119 samples have been tested as on May 26, 9 am and 92,528 samples have been tested in the last 24 hours, ICMR officials said.
India is the tenth most affected nation by the pandemic after the US, Russia, UK, Spain, Italy, Brazil, Germany, Turkey, and France, as per the John Hopkins University data.
The country has recorded 6,088, 6,654, 6,767 and 6977 cases on May 22, 23, 24 and 25 respectively. Also, the number of RT-PCR tests for detection of COVID-19 in the country crossed the 30-lakh mark on Monday.
The first two phases of the lockdown led to 14-29 lakh COVID-19 cases being averted, while the number of lives saved in that period was between 37,000 and 78,000, the government said last Friday, citing various studies, and asserted that the unprecedented shutdown has paid "rich dividends" in the fight against the pandemic.