NEW DELHI - Is a third wave inevitable? That is the question many are asking as an easing of Covid-19 restrictions has led to overcrowding at holiday destinations and marketplaces, even as the authorities warn that the next 100 days would be crucial for India's battle against the virus.

Health experts and epidemiologists believe a third wave of the pandemic is coming in the absence of strictly enforced mask-wearing and social distancing, especially if the virus mutates further.

"A third wave is expected anywhere between August and October, according to various Indian modellers. The presence of highly infectious variants, free movement and crowding of people and large numbers of unvaccinated people will create the third wave. If we observe Covid-19-appropriate behaviour and prevent superspreader events, we can limit it to a ripple, rather than a tidal wave," said Professor K. Srinath Reddy, president of the Public Health Foundation of India.

"If we are lax, we will suffer a severe surge. Some, but not all, of the adults infected in the past six months and those who are vaccinated will be protected. While the number of susceptible persons left in the population will be less than at the beginning of the second wave, there are still (many) who are vulnerable to infection and clinical disease."

India had a devastating second wave with the emergence of the more transmissible Delta variant earlier this year, with over 400,000 cases and 4000 deaths daily at its peak. The health sector struggled to cope with shortages of hospital beds, oxygen and medicines.

The government faced criticism for not doing enough and allowing large gatherings.

Religious gatherings have come under focus with the Supreme Court on Friday (July 16) asking the state of Uttar Pradesh to reconsider a decision to allow an annual Hindu pilgrimage called the Kanwar Yatra, in which devotees walk barefoot to pilgrimage sites. The state cancelled the pilgrimage.

The Indian Medical Association also warned against opening things up too fast.

"Tourist bonanza, pilgrimage travel, religious fervour all are needed, but can wait for a few more months. Opening up these rituals and enabling people without vaccination to go scot-free in these mass gatherings are potential superspreaders for the Covid-19 third wave," said the association in a statement.

Speeding up the vaccination drive is seen to be crucial to blunt the impact of any further waves of the pandemic.

Over six months, India has administered 395 million doses, with 5.6 per cent of the population fully vaccinated and 17 per cent partially vaccinated.

The country is now averaging four million vaccinations a day. But to meet the target of vaccinating all those eligible by the end of the year, it needs to double the pace.

"If the third wave comes in August, this will play a role. By October, many more will be vaccinated," said Prof Reddy.

While India has seen a decline in cases, there have been areas of concern. According to the health ministry, at least 47 of India's 718 districts have positivity rates of more than 10 per cent, with increases seen in the states of Kerala and Maharashtra.

"Analysis shows a projected decline in the use of face masks as we resume activities," said senior health ministry official Lav Agarwal.

But some epidemiologists believe India may not have to relive the intensity of the second wave.

Dr Jayaprakash Muliyil, an epidemiologist and former principal of the Christian Medical College in Vellore, said a third wave was not inevitable.

"The virus doesn't change much. These waves are a function of human behaviour. When you bring down a strong lockdown, you can produce a pause. The wave peak will be less, because for the virus to transmit, there should be unobstructed pathways. There are so many immune people, that pathway may break here and there," added Dr Muliyil.

"But if a new virus strain emerges... there will be a big wave around the world."