Date: Thu 25 Jul 2019 4:14 PM AEST
Source: Mirage News [edited]
The Department of Health today [25 Jul 2019] reported that an adult is currently recovering after being diagnosed with meningococcal disease serogroup W, bringing the number of reported cases of invasive meningococcal disease in 2019 to 13. Of the 13 cases, 3 have been serogroup B, 5 serogroup W, and 5 serogroup C meningococcal infections.
Meningococcal disease is an uncommon, life-threatening illness caused by a bacterial infection of the blood and/or the membranes that line the spinal cord and brain, and occasionally of other sites, such as the throat, lungs or large joints.
A total of 41 cases were notified in WA [Western Australia] in 2018. This was less than the 46 cases notified in 2017, but well above the long-term average for annual cases. The number of serogroup W cases in 2018 (30) was also the highest reported in any year.
A vaccine to protect against 4 serogroups of the meningococcal disease (serogroups A, C, W and Y) is offered free to all children in WA at 12 months of age, with a catch-up program for children who have not yet received the vaccine and who are aged 1-4 years. Due to a higher rate of meningococcal disease in Aboriginal people in WA, Aboriginal children are offered vaccination from age 6 weeks to 4 years of age. In addition, the vaccine is offered to all teenagers in Year 10, with a catch up program for 15-19 years.
[_Neisseria meningitidis_, the cause of meningococcal disease, 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. The average incubation period is 4 days but can range between 2 and 10 days.
Immunity following use of a meningococcal capsular 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 capsular 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 the UK following the introduction of C vaccine and serogroup A in the African Meningitis Belt following A vaccine, only to be replaced by emergence of disease due to other meningococcal serogroups.
MenACWY vaccine is also strongly recommended, but not funded, for: infants younger than 12 months of age; adolescents and young adults aged 20-24 years who live in close quarters or who are current smokers; Aboriginal and Torres Strait Islander people aged 2 months to 19 years; infants and children aged 2 months and older with medical conditions associated with an increased risk of meningococcal disease (additional doses and boosters required); and travellers to areas where meningococcal disease is more common (<http://ncirs.org.au/sites/default/files/2019-05/Childhood-schedule-table_May_2019_Final.pdf
The B vaccine is strongly recommended, but not funded, for: infants and children younger than 2 years of age; adolescents aged 15-19 years; adolescents and young adults aged 15-24 years who live in close quarters or who are current smokers; Aboriginal and Torres Strait Islander people aged 2 months to 19 years; and infants and children aged 2 months and older with medical conditions associated with an increased risk of meningococcal disease (<http://ncirs.org.au/sites/default/files/2019-05/Childhood-schedule-table_May_2019_Final.pdf
Western Australia, covering the entire western 1/3 of Australia, is mostly arid, its population being concentrated in the fertile southwest corner and its capital, Perth (<https://en.wikipedia.org/wiki/Western_Australia
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