It is too early to say if the Bath Half Marathon accelerated the spread of coronavirus, an expert has said.

At the time, organisers defended their decision – in line with Government advice at the time – to press ahead with the event on March 15 despite claims it would be a breeding ground for the disease and mounting calls for it to be cancelled.

Some 6,000 runners came to the city from across the country to take part, raising thousands for charity.

The deaths of 53 people at Bath's Royal United Hospital have been linked to Covid-19, nearly half of the total for Somerset, and the number jumped up in the two weeks after the race.

The Cheltenham Festival has been blamed for the relatively high number of cases in Gloucestershire.

But Dr Kit Yates, a senior maths lecturer at the University of Bath, said: "At the moment there is not enough data or evidence to say one way or another whether the Bath Half Marathon contributed in a significant way to the number of cases of coronavirus in Bath and the surrounding regions.

"It's certainly possible that a mass gathering of thousands of people when the virus was already circulating in the UK hastened its spread. By how much is difficult to say.

"How big an impact these potential extra cases would really have had, given that by that point the disease was already circulating in many parts of the UK, is debatable."

Dr Yates, author of The Maths of Life and Death, said the proportions of people being infected and dying in Bath does not look much higher than elsewhere in the country, and nonetheless it would be difficult to draw a definitive link to the half-marathon.

He said it may be possible "when the dust settles" to analyse the spread of the virus from how it mutates.

In Bath and North East Somerset, there are approximately 107 confirmed coronavirus cases for every 100,000 people, according to www.covidlive.co.uk.

In Gloucestershire the figure is 186 per 100,000.

Some have put that down to the Cheltenham Festival going ahead, attracting 250,000 people between March 10 and 13.

Leaked official data showed that a postcode next to the racecourse had the county's highest number of hospital admissions in early April.

Rather than being concentrated in one area, the Bath Half Marathon weaved through the city, starting and finished in Great Pulteney Street, taking in Upper Bristol Road, Newbridge Road and Lower Bristol Road.

Some 15,000 registered to take part but only 6,200 ran it. Many others chose to run a "virtual" half marathon amid concern about the virus.

In a letter to the Bath Chronicle, Brian Robertson said it was "madness" for the race to proceed and it could be a "a virus incubation cluster like no other".

But organisers decided it should go ahead, citing Public Health England guidance that the risk of infection from outdoors events was low, and said there was no medical reason why the race should have been cancelled.

A spokesman for Bath Half Marathon said this week: "We are not aware of any data or evidence suggesting a link between mass participation events such as the Bath Half and Covid-19.

"As such, in the absence of any such data these discussions are pure speculation, and should be addressed to the public health team.

"The decision to go ahead with this year's Bath Half Marathon was made after detailed consultations with and on the advice of the local public health team and our own race medical team, and followed the clear Government and Public Health England guidance at the time."

Bath and North East Somerset Council and the RUH declined to comment.