Organisers faced calls to postpone or cancel the event, including from Bath's MP, they but said it would go ahead as planned.
A total of 6,200 runners took part in the 13.1 mile race, about half the usual number expected.
Almost 1,000 people joined a Virtual Bath Half group on Facebook instead - running the distance in their own communities and posting about it online.
They have asked for organisers of the Bath Half Marathon to send medals to those able to prove they have completed the 13.1 miles.
The London Marathon, which was due to take place in April, has been postponed.
Speaking before the event, Bath MP Wera Hobhouse said it was "simply not worth the risk" and that serious concern about it had "risen very dramatically" among residents of the city.
"I understand how disappointing the cancellation would be for all those who have been preparing for weeks and months, however this is a public safety concern, and I believe that cancelling the event to protect the most vulnerable in our city from a further spread of the infection must be the priority," the Liberal Democrat MP said.
Organisers said they had "carefully considered, listened and consulted" before deciding that the half marathon would continue as planned.
They said the risk of infection from outdoor events remained low and there was “no epidemiological or medical evidence" to suggest it should currently be restricted.
"It is now too late for us to cancel or postpone the event," they said.
"The venue is built, the infrastructure is in place, the site and our contractors are ready. Runners are already arriving in the city, keen for the race to go ahead.
"Even if we were to cancel at this late stage on the eve of the event, we anticipate that thousands of runners would still turn up to run the route, and we feel we would owe a duty of care to those runners, given that our resources are ready and waiting to support them."