The number of cases of meningitis being investigated by health officials in the UK linked to Kent has risen to 20, up from 15 previously.
The UK Health Security Agency (UKHSA) said that, as of 5pm yesterday, some 20 cases of meningitis had been reported to it.
Of these, nine cases have been confirmed in the lab and 11 remain under investigation.
Six of the confirmed cases have been confirmed as the meningitis B (menB) strain.
A statement said: “All those affected who are currently linked to the outbreak are young adults.
“UKHSA is aware of a baby with confirmed meningococcal group B infection who is not currently linked to the outbreak but UKHSA will continue to investigate this case.”
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.
UKHSA chief executive Susan Hopkins said: “This looks like a super-spreader event, with ongoing spread within the halls of residence in the universities.
“There will have been some parties particularly around this, so there will have been lots of social mixing.
“I can’t yet say where the initial infection came from, how it’s got into this cohort, and why it’s created such an explosive amount of infections.
“I can say that in my 35 years working in medicine, in healthcare and hospitals, this is the most cases I’ve seen in a single weekend with this type of infection.
“It’s the explosive nature that is unprecedented here – the number of cases in such a short space of time.
“NHS were initially managing it as a major incident in the region but they have now increased that overlay to having a national-level oversight as well.”
All reported cases so far have been linked back to Kent
England’s deputy chief medical officer Dr Thomas Waite said: “This is by far the quickest-growing outbreak I’ve ever seen in my career, and I think probably any of us have seen, of meningitis for a very long time.
“Whilst it remains an outbreak that is having its consequences in Kent, it is obviously of national significance.”
About 5,000 students in university halls in Kent are to be offered the meningitis B vaccine in coming days. The aim is to prevent further disease in several weeks time if somebody has been harbouring the infection.
Four schools in total across Kent have now confirmed cases and hundreds of people are being offered antibiotics as an immediate treatment.
All reported cases so far have a link to Kent, according to the UKHSA.
At least one person who fell ill and had links to Kent attended a London hospital.
Scientists work to identify source of spread
Health officials stressed that people should not skip antibiotics if prescribed them, with a single tablet of Ciprofloxacin reducing the risk of meningitis in a household by about 80% to 90%.
Experts said many of those affected attended Club Chemistry in Canterbury over 5 March to 7 March.
The UKHSA said all 15 cases reported had required hospital admission, with four cases confirmed to have menB.
Laboratory scientists are urgently trying to work out if the spread is caused by a possible mutant strain of menB.
The genome of the menB strain identified in the outbreak is undergoing whole genome sequencing to see if there are any differences to known strains.
It will also be tested against available menB vaccines, though experts stressed people should get a jab if eligible.
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Earlier yesterday, UK Health Secretary Wes Streeting said most students would not already be vaccinated against menB, adding that the jabs will begin in the next few days.
He told MPs: “This is an unprecedented outbreak. It is also a rapidly developing situation.”
He said the menB vaccine has been available on the NHS since 2015 as part of routine childhood immunisations, “but clearly most students would not be vaccinated”.
He added: “Given the severity of the situation, I can confirm to the House that we will begin a targeted vaccination programme for students living in halls of residence at the University of Kent in Canterbury, which will begin in the coming days.”
The programme may also expand further if other groups are deemed to be at risk.
Mr Streeting said he had asked the Joint Committee on Vaccination and Immunisation to “re-examine eligibility for meningitis vaccines” for a wider group of people after it ruled a menB catch-up campaign for older children was not cost-effective.
The Health Secretary also told MPs he was “confident” that the UKHSA acted as “quickly and comprehensively as possible” in its response to the outbreak of meningitis, after criticism that it was too slow to act and inform the public.
Mr Streeting also set out how the cases “link back” to the Club Chemistry nightclub over the dates of 5 March and 7 March.
He said that on Saturday, French authorities alerted the UKHSA to a confirmed case in France in a person who had attended the University of Kent.
Both two cases at this point lived in private accommodation, “and at that stage, there was no apparent link between the two”, Mr Streeting said.
There are four centres open in Canterbury offering antibiotics, with 11,000 doses available on site, Mr Streeting told MPs.
“The onset of illness is often sudden, and early diagnosis and treatment with antibiotics are vital,” he said, adding it could likely be spread from sharing drinks, vapes and close contact.