"As we have started unlocking, there is again a lack of Covid-appropriate behaviour. We don't seem to have learnt from what happened between the first and the second wave. Again crowds are building up... people are gathering. It will take some time for the number of cases to rise at the national level. A third wave is inevitable and it could hit the country within the next six to eight weeks... maybe a little longer," Dr Guleria told NDTV. "It all depends on how we go ahead in terms of Covid-appropriate behaviour and preventing crowds," he added.
Many parts of the country, including cities such as Delhi and Mumbai, earlier ravaged by the spread of the virus and under strict lockdowns, have lifted their lockdown and curfew restrictions this month, as Covid cases have declined steadily across the country. In the last 24 hours, India recorded 60,753 new Covid cases and 1,647 deaths because of the virus. The daily positivity rate is 2.98 per cent — the 12th consecutive day it has remained below 5 per cent.
Guleria added that vaccination remains the core weapon against the virus and increasing the gap between the two doses of the Covishield vaccine “may not be a bad approach” to provide more people with protection.
"Vaccination is the main challenge. A new wave can usually take up to three months but it can also take much lesser time, depending on various factors. Apart from Covid-appropriate behaviour, we need to ensure strict surveillance. Last time, we saw a new variant - which came from outside and developed here - led to the huge surge in the number of cases. We know the virus will continue to mutate. Aggressive surveillance in hotspots is required," the AIIMS chief added.
On the spread of the Delta variant in the United Kingdom, which is now facing a third wave, he said, "Virus is still mutating, we need to be careful".
The highly transmissible variant first identified in India is now making up 99 per cent of fresh COVID-19 cases in the UK, news agency PTI reported.
The number of Delta variant infections has jumped by 33,630 in a week to hit a total of 75,953 in the UK, with the highly transmissible variant first identified in India now making up 99 per cent of all COVID-19 cases in the country, health officials warned on Friday.
Public Health England (PHE), which has been tracking variant of concerns (VOCs) on a weekly basis, said its data shows an increased risk of hospitalisation with Delta VOC compared to Alpha the VOC first detected in the Kent region of England.
It also pointed to its previous findings that two doses of a COVID vaccine gives a "high degree of protection" against hospitalisation from the Delta variant.
The gap between the new waves is shortening and it's 'worrying', Dr Guleria said.
"During the first wave (in India), the virus was not spreading that rapidly... all that changed during the second wave, and the virus became much more infectious. Now the Delta variant that's spreading is much more infectious. Faster spread is likely," said the AIIMS chief.
On the Delta plus variant, the AIIMS chief explained: "We need an aggressive genome sequencing to see how the virus is behaving. Does the vaccine efficacy come down, does the monoclonal antibody treatment work? To do all of that, we need to have a large or very good network of labs to study the data. I think that's where to move in the next few weeks. And that's the new frontier we need to develop if we want to succeed in our fight against Covid."
Guleria reiterated that till now, there is no evidence to suggest that children will be affected more in the next wave of the infection.
Earlier, India's epidemiologists had indicated that a third wave of COVID-19 is inevitable and is likely to start from September-October.
India was hit severely by a brutal second wave of the COVID-19 pandemic in April and May, claiming a massive number of lives daily, with shortage in oxygen supply at various hospitals adding to the woes.
However, the number of cases have shown a downward trend and the positivity rate too has been shrinking in the last several days. From a daily case count of over 4 lakh, the number of new COVID-19 cases has been hovering around 60,000 in the last couple of days.
There needs to be aggressive surveillance strategy in Covid hotspots and lockdowns in case of any significant surge. The moment a significant surge in cases in noted in a particular area and the positivity rate goes beyond 5 per cent, area-specific lockdown and containment measures should be implemented, he said.
"However, a national-level lockdown cannot be a solution (to rein in the pandemic) keeping economic activity in mind."
With 60,753 new Covid cases being reported in a day, India's total tally rose to 2,98,23,546, while the number of active cases stand at 7,60,019, the lowest in 74 days, according to Union health ministry data updated on Saturday.
The death toll climbed to 3,85,137 with 1,647 fresh fatalities and active cases comprise 2.55 per cent of the total infections, while the national COVID-19 recovery rate has improved to 96.16 per cent, the data updated at 8 am showed.
On Friday, a Reuters poll of medical experts said that the third wave of Covid infections in India is inevitable and could hit the country by October this year. The 40 healthcare specialists from around the world who took part in the survey added that the third wave will be better managed than previous outbreaks, considering the increase in the pace of vaccinations in India. However, they added that Covid-19 will remain a major public health concern in India for at least another year.