At least 12 groups of Neisseria meningitidis have been identified and of these A, B, C, Y and W (previously called W-135) are the most likely to cause disease. Patterns of infection differ throughout the world. Although group A is the most common cause of meningococcal disease worldwide, in New Zealand, group B is most likely to cause disease (around two-thirds of cases in 2016). In 2016, around one in ten cases of meningococcal disease were caused by groups C, Y and W. Disease caused by group A occurs infrequently in New Zealand.
An increase in meningococcal disease cases caused by a very virulent Neisseria meningitidis group W sequence type (ST–11) has been seen in Canada over 2014–2016 and in Australia and the United Kingdom (UK) over 2016–2017. Clinical illness with the hypervirulent meningococcal strain tends to be severe. Overall case numbers of meningococcal group W are still low in New Zealand. However, there is a trend showing an increase in disease caused by meningococcal group W, including cases of the hypervirulent group W type ST–11, over 2016 and 2017.
Isolated outbreaks of meningococcal groups A and C have occurred in New Zealand: the last group A outbreak was in 1985/86 in Auckland, and the most recent group C outbreak was in Northland during 2012. During 1991-2007, a New Zealand-only strain of group B caused an epidemic. The epidemic mainly affected under-one year old Māori and Pacific infants and children aged 1–4 years of other ethnicities. The rate of meningococcal disease in 2014 was the lowest since 1990.
How you get it
Meningococcal bacteria are commonly carried in the nose and throat, and do not usually cause disease. Carriage rates are highest in older teenagers and young adults. The bacteria can be transferred from person to person through contact with saliva, e.g. intimate kissing. In rare cases, the bacteria can invade and rapidly lead to severe disease. The underlying reasons for why invasion occurs in some individuals are not well understood.
Who is at risk?
In New Zealand, infants and children aged under 5 years and adolescents aged 15–19 years have an increased risk of meningococcal disease. Māori, particularly infants aged under 1 year, and Pacific peoples have a higher risk of meningococcal disease than other ethnic groups.
What increases the risks?
- Exposure to tobacco smoke, binge drinking, or having another respiratory infection, e.g. influenza.
- Living in close proximity to others, e.g. in a crowded household, at boarding school, in university halls of residence, or in long-term institutional care.
- Being in a household or other close contact of someone carrying the bacteria or with the disease, e.g. those who have been intimate, or infants and children attending an early childhood education centre.
- Having a medical condition or receiving treatment that affects the immune system, e.g. the person has had their spleen removed, or taking disease modifying immunosuppressive medication.
- Age and ethnicity.
The initial symptoms are difficult to distinguish from other infectious illnesses, particularly flu-like illnesses. Symptoms usually progress quickly to a severe illness, often within 24 hours.
- Infants may have: a more gradual onset than adults, fever, cry, appear unsettled, feed poorly, vomit, be sleepy or hard to wake, dislike bright light, or have a rash or spots. They may have a bulging fontanelle.
- Older children and adults may have: a fever, malaise, nausea, vomiting, muscle aches and pains, drowsiness, headache, dislike of bright light, neck stiffness, or have a rash or spots.
Almost 80% of cases will develop a rash that does not blanch (become pale/go white) when pressed on. This type of rash is often a late sign of infection.
Individuals with disease caused by the very virulent meningococcal group W ST-11 type may present with atypical symptoms, including gastrointestinal symptoms.
What are the risks?
If meningococcal bacteria pass into the blood, the disease usually progresses very quickly. A person with meningococcal disease may develop:
- Meningitis (inflammation of the membranes around the brain)
- Septicaemia (blood infection)
- Pneumonia (lung infection)
One to two people out of every ten who survive meningococcal disease have long term complications, such as extensive skin scarring, amputation of limbs and extremities, hearing loss, seizures or brain injury
Even when the disease is identified and treated early 1–2 people in 10 will die.
Prompt diagnosis, early administration of injected antibiotic to patients suspected of having meningococcal infection and immediate admission to the hospital may help to decrease the risk of permanent damage and death.
The risk of infection for household contacts of a person with the disease is highest during the first seven days and may persist for many weeks. Preventive antibiotics should be administered to close contacts as soon as possible, preferably within 24 hours of identification of the person with meningococcal disease.
During an outbreak, a meningococcal immunisation programme may be commenced for those in the highest risk groups if a vaccine is available. Meningococcal conjugate vaccines reduce the number of people carrying N. meningitidis in the back of their throat thereby reducing the spread of the bacteria around the community. This contributes to ‘herd immunity’ while protecting the individual from invasive disease.
Vaccines that protect against meningococcal disease have been available since the 1970s but none protect against all the groups that cause disease. There have been vaccines against the groups A, C, Y and W for more than 20 years but it has taken much longer to develop vaccines that protect against the different types of meningococcal group B. Please refer to the IMAC factsheet on available meningococcal vaccines.
Complications of disease
Responses to meningococcal vaccines
Menactra®, NeisVac-C®, Nimenrix®
As with any medicine, very rarely, severe allergic reactions occur following immunisation
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