Top doctors have warned elite runners are taking a major health risk by competing in Sunday's New Delhi half-marathon in the midst of a major coronavirus outbreak and soaring air pollution.
Women's marathon world record-holder Brigid Kosgei from Kenya and Ethiopia's two-time men's winner Andamlak Belihu are among the 49 elite athletes running the 21-kilometre (13.1 mile) race, while thousands of amateurs are taking part virtually.
Organisers say the "highest level of safety-standards, with bio-secure zones" have been laid on for the race starting at the Jawaharlal Nehru Stadium.
But with New Delhi recording more than 500,000 virus cases, and air quality in the world's most polluted capital hovering between 'unhealthy' and 'hazardous', health experts said the athletes should think twice.
"It will be suicidal for runners to run the race this time. We have such high levels of pollution, we have the risk of coronavirus," Arvind Kumar, founder trustee of the Lung Care Foundation, told AFP.
"With the presence of this twin threat if people are still running despite knowing everything, well, I have no words to express my anguish."
"Whether you are an international elite runner or you are a small boy from a village, the damaging potential of a damaging agent remains the same," said the doctor.
Randeep Guleria, director of the All India Institute of Medical Sciences (AIIMS), the country's top research body, told AFP that "in an ideal situation" the race should not be run.
"Because of high levels of air pollution, exercising outside in this weather sometimes can lead to aggravation of underlying lung problems," he said.
"Even if you are an elite runner the air pollution would still affect your lung."
Normally thousands of amateurs would also take part, but because of the coronavirus they have been told to run their chosen route between Wednesday and Sunday and chart their time on an app.
Delhi has been hit by a winter pollution crisis each year for the past decade when crop-stubble burning from nearby states, cold temperatures and car and industrial pollution produce a toxic mix.
This year, the Indian capital is also a major concern in the battle against the coronavirus. India is the world's second worst-hit country behind the United States, with about 9.3 million cases.
The city is considering imposing a night-time curfew because of the rising number of cases, according to media reports.
Kosgei, who is visiting India for the first time, acknowledged her concerns about travelling for the race.
"We have definitely been affected by COVID-19. I had to convince my parents and family back home to allow me to visit Delhi for the half-marathon," she said.
"The virus has affected most of the sporting events. But it is important for us to take care of ourselves."
As in other countries, nearly all sport in India has been cancelled.
After repeated delays, the Indian Premier League cricket went ahead in the United Arab Emirates and the Indian Super League football is being held in a bio-secure "bubble" in Goa.