MUMBAI (NYTIMES) - So far, India has had to contend with very few known cases of coronavirus. And its leaders are determined to try to keep it that way.

On Thursday (March 19) evening, in a prime-time speech to the nation, Prime Minister Narendra Modi urged his 1.3 billion citizens to "avoid crowds and stay at home".

"Today, what is known as 'social distancing' is very necessary," Mr Modi said.

Earlier in the day, the authorities also announced a week-long ban on incoming international flights, beginning on Sunday.

The prime minister's appeal came just in time in the northern state of Uttar Pradesh, where the authorities face an urgent challenge: Dissuading hundreds of thousands of Hindus from travelling there next week for a nine-day celebration of Ram, one of the religion's most important gods.

Devotees believe Ram, also known as Rama, was born in the Uttar Pradesh city of Ayodhya, and for generations, they have descended upon it for his birthday festivities.

This year, they run from March 25 to April 2, and this time, pilgrims plan to celebrate the start of construction of a new Ram temple in Ayodhya.

Now their faith is colliding with the coronavirus pandemic, which has infected just 173 people in India, according to government data, even as it sickened more than 218,000 people and killed more than 9,000 worldwide.

"We need to stop this crowd from gathering," Dr Ghanshyam Singh, chief medical officer of Ayodhya, told reporters earlier this week.

Public health experts say that large crowds, in which people are unable to keep at least 1.8m apart, pose a high risk for transmission of the virus.

Religious festivals, Dr Singh noted, come and go, but public health is paramount. "If life is not there, then there are no celebrations," he said.

The conflict between religion and health has put the government of Uttar Pradesh - India's largest state, with 230 million people - in a difficult bind.

For several days, officials have been trying to dissuade people from gathering in Ayodhya without actually taking the politically volatile step of forbidding them to do so.

Dr Siddharth Nath Singh, a state Cabinet minister who until last August oversaw health issues, said the government had reached out to the main organiser of the festival, the Vishva Hindu Parishad (VHP), and other religious leaders to ask that the devout worship Ram at home this year.

"In matters of faith, the persuasion is best done by religious gurus," Dr Singh said in an interview on Thursday. "Already, the VHP is making requests that people should not come out. In their own house, they should hold prayers."

Led by a tough-as-nails Hindu monk, Yogi Adityanath, Uttar Pradesh is a key pillar of political support for Mr Modi and for the Hindu nationalist party that he leads, the Bharatiya Janata Party (BJP), to which Mr Adityanath belongs.

About 80 per cent of Indians are Hindu, and the BJP has sought Hindu votes for years, with the promise of building a Ram temple in Ayodhya, where a Muslim mosque stood until a Hindu mob destroyed it in 1992, setting off deadly riots.

Last November, the Supreme Court settled decades of legal disputes and gave the site to the Hindus.

Mr Adityanath, who has supported other mass pilgrimages such as last year's Kumbh Mela, is supposed to help kick off the Ram festival.

On Tuesday, just before the event formally begins, he is scheduled to participate in a ceremony to move a revered idol of Ram from a tent to a bulletproof enclosure near the planned new temple.

Late on Thursday night, Mr Adityanath's office urged the state's residents to perform religious services at home to prevent the spread of the virus.

Mr Vinod Bansal, a national spokesman for the VHP in New Delhi, said that his group was not directly telling worshippers to go to Ayodhya, but that "people go there uninvited from all over the world".

"People are getting the opportunity to have glimpses of Lord Rama," he said. "It's not appropriate to deprive them of this opportunity. That will be very difficult."

Officials in Uttar Pradesh have said that if the pilgrims come, it is prepared with thermal monitors, 100,000 face masks and 4,000 litres of hand sanitiser, according to Newslaundry, an Indian news site.

Prof John Ioannidis, a professor of medicine and biomedical data science at Stanford University, said that if the Ayodhya festival is allowed to proceed, the government could consider asking people to voluntarily be tracked and tested for the virus a few weeks later.

"We know very little about what's happening with the virus," he said. "We need data. I'm sure that among one million people, there would be volunteers who would be willing to be tested."

Mr Modi's national call for Indians to stay home, however, may well reduce the flow of pilgrims to a trickle.

"I appeal to all of you: For the next few weeks, step out of your homes only when absolutely necessary," the prime minister said.

Mr Bansal, the VHP spokesman, was hopeful that everything would work out fine for the Ayodhya pilgrims.

"The local administration and temple trust will decide how these events are conducted smoothly," he said. "Lord Rama will also help."