Likewise, the chance of a Covid-19 positive person being at a 50-person gathering in Somerset is just one in eight (13 per cent), versus an almost nine in ten (86 per cent) risk in Liverpool.
The model, originally designed to demonstrate the dangers of large gatherings during the US football season, has been expanded to display the risks of event sizes across the UK, Italy and Switzerland.
Joshua Weitz, Prof of biological sciences and physics at Georgia Tech, who helped create the map, said it could be used by individuals to decide if they want to visit a local pub or restaurant, or by policymakers to impose more localised lockdowns.
“If you know that there was a one in four chance… that someone in that pub or restaurant, or gathering had Covid-19… I would hope that would change someone’s behaviour,” he said
He also said that areas with a lower risk should not think they have “carte blanche” to meet in very large groups without mask wearing.
“That will only again facilitate more spread,” he added.
“But it does imply that depending on the region there are absolutely different risk levels (for) large gatherings and that really does reflect ongoing and heterogeneous differences in circulating infections.”
The scientists used local authority data from Public Health England (PHE).
Elsewhere, the risk of encountering someone with Covid-19 at a 50-person event in Blackburn with Darwen, for example, is around four times higher than in Bromley (85 per cent versus 23 per cent).
While the chance of someone having the virus at a 50-person gathering in County Durham is around 50 per cent higher than in Suffolk (18 per cent versus 67 per cent).
In Lancashire, the risk of a Covid-19 positive person being present at a 25-person event is more than double that of neighbouring North Yorkshire, 47 per cent versus 20 per cent.