Covid infection rate for 20 - 24 year-olds in Wakefield 'doubles' in just two weeks
Mild symptoms and the nature of work for young adults have been identified as possible causes behind the spike.
The rate of infection across all age groups in the district has risen to just over 21 cases per 100,000 people - an average of around 74 cases per week.
Wakefield remains classed an "area of concern" by the government and the council's leader has acknowledged a local lockdown is possible.
But speaking to a virtual health scrutiny meeting on Thursday, Stephen Turnbull, from Wakefield's public health team, said he was "concerned but not alarmed" by the figures.
He explained that the overall rise was being driven by growing case numbers among young adults.
He told councillors: "On August 12, 20 - 24 year-olds made up about seven per cent of all cases ever seen in Wakefield.
"Over the last two weeks that's grown to 14 per cent. So the infection rate in 20 - 24 year-olds has doubled. That's where the increase is.
"The people in this age group, very often, are fit and healthy. They'll have a very mild Covid experience.
"They may have a mild cough or a fever and then they'll get better.
"What we're concerned about is they don't just socialise or work with their own age group. They may have elderly relatives, they may work in a care home or they may have had two or three jobs.
"That's why we're seeing more infections."
Local Democracy Reporting Service