The number of cases of meningitis linked to an outbreak in Kent in England has risen to 29, up from 27 previously, the UK Health Security Agency (UKHSA) has said, including both confirmed and suspected cases.
The agency said in a statement that, as of 12.30pm yesterday, it had been notified of 18 confirmed and 11 probable cases of meningitis linked to Kent.
Some 13 of the 18 confirmed cases are meningitis B. All cases have required hospital admission, it said.
It comes after one school pupil and one university student died from the infection and some young people have been placed in induced comas.
The chief scientific officer of UKHSA, Professor Robin May, said experts are still trying to work out if the meningitis bug has become more transmissible in the recent cases.
He told Times Radio: "It's certainly very unusual. So typically, we see on average in the UK about one case of meningitis a day. This is obviously a much bigger number than that and so there's something unusual about this outbreak.
"We are focusing our investigations on two possibilities, which both may be true, or neither.
"So one is that there is something about the particular setting that has enabled this bacteria to spread very well in that particular club setting. We don't know that, there's no evidence for that at the moment, but that's one course of investigation.
"The other possibility is that the bacteria itself has changed in a way that makes it more transmissible, perhaps more likely to cause disease.
"Many of us carry menB as a bacteria without any problems in the back of our throats all the time. So it could be that this is a bacteria that's just more likely to progress to disease.
"We don't know that - we've been working, as you can imagine, around the clock since the discovery of this outbreak to try and understand more about it, including doing DNA sequencing, genome sequencing for this strain and that is due back very, very soon. That analysis is extremely complex. The genome for this bacteria is about 100 times bigger than Covid so it's a lot more complicated.
"So it will take us some time to analyse that, but we are very much focusing our attention on whether anything has changed in the bacteria that might make it more likely to spread or cause disease."
Asked if such an outbreak could happen again, he said: "Well obviously that's something we're very conscious of."
He said "we'll be mindful both of the possibility of this particular strain, for example, re-emerging in the future, but also general principles that we'll learn about the bacteria.
"As with all pathogens, there's always much more we can learn, and by learning more about how they work, we hope to develop better ways to prevent them causing disease in the future," added Prof May.
HSE liaising 'regularly' with UKHSA
Dr John Cuddihy, Health Service Executive National Director for Public Health, said the HSE public health team has been liaising "regularly" with its UK Health Security Agency "colleagues" about the outbreak.
Dr Cuddihy said on RTÉ's News at One that most of the cases in the outbreak are students from University of Kent in Canterbury and some local secondary schools.
He said that while the UK health authorities have warned that the situation is "evolving and further cases are possible," the HSE also "liaises closely" with the European Centre for Disease Control.
He said the ECDC's "threat assessment" in relation to the outbreak "indicates" that the risk of "invasive meningococcal disease cases to the general public in EU and EEA countries, including Ireland, is very low."
Dr Cuddihy said this assessment was "due to the very small probability of exposure to potential infection outside of this outbreak in Kent."
He said the "MenB" vaccine has been part of the free national child and immunisation schedule for babies born from 1 October 2016.
Dr Cuddihy said there is currently no "catch-up programme" over the age of 2 in Ireland, however the "prevalence of this MenB disease is highest in babies under 1 (years of age)."
"And in that way, the primary vaccination schedule aligns very well with the prevalence."
He said it was "really important" for parents and guardians to check that their babies and young children are "up-to-date" with their childhood vaccinations.
Dr Cuddihy added that the HSE also administers "MenACWY" vaccine for other strains of meningitis in first year of secondary school.
He urged parents to "watch out" for the consent forms "coming home in school bags" and to make sure that school children avail of those vaccines as well.
