Date: Mon 18 Feb 2019
Source: Independent [edited]
A rare form of deadly meningitis is on the rise in Ireland following a pattern seen in other countries, disease specialists have revealed. The number of cases of the [_Neisseria meningitidis_ serogroup] W strain has increased from one in the year 2014 to 12 last year . There has also been an increase in [meningococcal] meningitis [serogroup] Y over the same period, up from 3 to 8 (See: <http://www.hpsc.ie/news/newsarchive/2019newsarchive/title-18757-en.html
Neither strain is currently included in the vaccines to protect against meningitis [that] are commonly given to children.
The increase follows a similar trend in the Netherlands and the United Kingdom, which has in turn led to the MenACWY vaccine now being offered by health services to teenagers and college and university students.
No such vaccination programme has been introduced here yet, but the rise in cases will have to be examined by the group of experts which advises the HSE [Health Service Executive] on what jabs should be given free to various groups of patients.
Like other forms of the disease, it can be very serious if not treated quickly with antibiotics. Without emergency treatment, it can lead to life-threatening blood poisoning, and result in permanent brain or nerve damage.
The report [source?] from the Health Protection Surveillance Centre, the country's disease watchdog, said that during January  there were 17 cases of different forms of meningitis. Four of these involved the W and Y strains. Two people died from meningitis during January . Overall, the incidence of meningitis in Ireland has fallen in the past 2 decades.
In the past, the meningitis B and C strains presented the highest risk, but the introduction of vaccines for both has led to a fall in circulation of both.
The report pointed out that in 2000, the meningitis C vaccine began to be routinely given to children, which went along with a catch-up programme for teenagers. Since the introduction of the meningitis C vaccine, the annual incidence of the strain has decreased substantially from 135 cases in 1999 to 20 last year .
A vaccine to protect against meningitis B was introduced in recent years, but only for children born after October 2016, leaving parents of older children to pay Euro 300 [USD 340] to have the jab privately. The annual incidence of meningitis B has also reduced considerably from 292 cases in 1999 to 46 cases in 2018.
The report said that changing trends in the incidence of the infection have been reported in other European countries in recent years. In Italy, the number of meningococcal W cases has been increasing since 2013. "The Netherlands has also seen an increase in reported cases of meningococcal W cases, which had been very rare prior to 2015. Between 2010 and 2014, an average of 4 cases of meningococcal W were reported annually but increased substantially over the following years to 80 cases in 2017. "This rapid upsurge in meningococcal W in the Netherlands has been attributed to a meningococcal W," it added.
The report said that 17 cases and 2 related deaths were reported from 1-29 Jan this year . "This was slightly less than in the same period last year when 19 cases -- and 2 related deaths -- were notified. "Amongst the 17 cases notified from 1-29 Jan 2019, different strains were reported, and different age groups were affected."
The report added that although meningitis notifications have been stable in the 1st 4 weeks of 2019 compared to the previous year , ongoing monitoring of trends is needed "to assess the circulation, distribution and evolution of specific control strategies, particularly preventive vaccination programmes, and to inform national vaccination policy." [Byline: Eilish O'Regan]
[A recent (23 Jan 2019) report from the Health Protection Surveillance Centre (HPSC) gives numbers of cases that are slightly different from the news report above for a similar period of time (<http://www.hpsc.ie/news/newsarchive/2019newsarchive/title-18757-en.html
>): "Twenty meningococcal cases were notified to HPSC in Ireland between 24 Dec 2018 and 22 Jan 2019, compared with 19 cases in the same period last year . There is not an outbreak. Meningococcal disease is known to have increased incidence in winter and early spring. Among the 20 cases, different age groups were affected, different strains were reported (B,C,W,Y), different regions of the country reported the cases and there were no links found between the cases. Sadly, 3 of the cases have died; none was caused by meningococcal strains that are covered by the vaccines in the national childhood programme (the strains were not B or C)."
_Neisseria meningitidis_ only infects humans; there is no animal reservoir, and the organism dies quickly outside the human host. _N. meningitidis_ colonizes the mucosal membranes of the nose and throat; up to 5-10 percent of a population may be asymptomatic nasopharyngeal carriers, but the carrier rate may be higher in epidemic situations. Droplets of nasopharyngeal secretions from these carriers are responsible for the spread of the disease. Close and prolonged contact with an infected person or a carrier facilitates the spread of the disease.
Several meningococcal vaccines are available. Immunity following use of a meningococcal polysaccharide vaccine is specific for the type of capsular polysaccharide that the vaccine contains, with no cross-protection against infection due to other meningococcal polysaccharide groups. Although there are at least 13 _N. meningitidis_ serogroups, based on the antigenic specificity of their capsular polysaccharides, disease due to serogroups A, B, C, Y, and W are most common.
There are vaccines that contain capsular polysaccharide (A, C, Y, W), either alone or conjugated to protein. Conjugate vaccines are preferable, because, unlike the polysaccharide vaccines, conjugate vaccines immunize infants, reduce the carriage of meningococci in the throat and thus its transmission, as well as confer a more sustained immune response, and, therefore, longer-term protection than the polysaccharide vaccines. Serogroup B vaccines are based upon meningococcal B protein antigens, because group B polysaccharide is poorly immunogenic in humans and is a potential auto-antigen.
Following the mass introduction into the population of a vaccine specific for one particular serogroup, the incidence of disease due to that serogroup has been found to fall dramatically, e.g., serogroup C disease in several countries (e.g., UK, Netherlands, and Australia) following the introduction of conjugate C vaccine and serogroup A in the African Meningitis Belt following conjugate A vaccine, only to be followed by the emergence of a "replacement" pathogen, e.g., serogroup W. in subsequent years.
Because of the continuing rapid increase in the UK in serogroup W disease, the UK replaced the adolescent meningococcal C conjugate vaccine for 13-14-year-olds with the quadrivalent ACWY conjugate vaccine in the autumn of 2015. In addition, catch up campaigns were set up to give the ACWY vaccine to all 13-18-year-olds and new university admissions during 2015 to 2017 (<https://www.rivm.nl/bibliotheek/rapporten/2017-0031.pdf
Neither B nor ACWY vaccinations were included in the Dutch National Immunisation Programme. However, as of May 2018, the meningococcal ACWY vaccination replaced C vaccination at age 14 months and from October 2018, 13-14 year olds were offered ACWY vaccination (<https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5915972/
>). A detailed discussion of these issues in the Netherlands appears in a publication "Meningococcal disease in the Netherlands. Background information for the Health Council. RIVM Report 2017-0031 M.J.Knol et al," which is available at <https://www.rivm.nl/bibliotheek/rapporten/2017-0031.pdf
>. - ProMED Mod.ML]
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