The number of cases of meningitis being investigated by the UK Health Security Agency (UKHSA) in Kent has risen to 20, up from 15 previously, the body said on Wednesday.

Thousands of students in Kent are to be offered vaccines in the coming days as health chiefs deal with an “unprecedented” and “explosive” outbreak of meningitis.

The number of cases is expected to rise because the incubation period for the infection – to when symptoms appear – is two to 14 days.

The outbreak is being viewed by experts as unprecedented owing to the high number of cases appearing in such a short space of time.