The return of thousands of students to Bath's two universities will inevitably lead to an increase in coronavirus cases, the city's public health boss has warned.

Dr Bruce Laurence said he "completely supports" the reopening and noted that a lot of planning had been put in place by the University of Bath and Bath Spa University to ensure they are as safe as possible.

Covid-19 cases are growing at the fastest rate in younger people.

Dr Laurence, the public health director at Bath and North East Somerset Council, said it could be because they are mixing more, or because they are more likely to be frontline workers, while older residents have become more risk-averse.

He told scrutiny panel members yesterday (September 15): "Case numbers are rising in Bath and North East Somerset, as elsewhere.

"We're facing a possible second increase. We will certainly see an increase through the autumn and winter.

"We're facing risks from opening up schools and universities, but a lot of work has gone into doing them as safely as possible. Everything you do that brings people together creates risk.

"There are two ways to look at it. You'll have cases, and you'll have illness and death. So far we've had an increase in cases without very much increase in serious illness and death.

"The increase in cases has been seen much more in people in their 20s, then 30s, then teens. Older people have been affected, but much less so. The worry is at what point will it spread through the generations.

"We need to prepare. We will continue to be cautious. If we don't control outbreaks we're going to lose it."

He added: "One of the things that will put our cases up – although I completely support universities starting, I'm absolutely not against it – but inevitably that will be a place where we start to get cases.

"Hopefully not illness or death, but we have to expect that, having a lot of people coming in. A lot of planning has been done. Hopefully we will still be at the low end."

The University of Bath has identified sites in the city and on campus that could become coronavirus testing centres should there be a rise in cases. It will also have hundreds of rooms available to students who may need to self-isolate after traveling.

Bath Spa University has similar measures in place and has come up with a way people can report the behaviour of its students in relation to coronavirus.

Last year the two universities had some 25,000 students enrolled.

Asked why the number of cases was rising faster than the number of people contracting serious illness or dying, Dr Laurence said: "Younger people are mixing more, perhaps because they're less careful, perhaps because they're the frontline worker age and live in close proximity.

"Older people have become more risk-averse, they may be self-shielding to some extent.

"Treatments are getting better. We're wondering if the virus is changing its behaviour. I've heard rumours it may be getting less dangerous.

"In the beginning saving the NHS overruled everything else and people were moved to care homes, where it was too early, and they seeded infection. That's a mistake we won't make again."