At least 13 groups of Neisseria meningitidis have been identified and of these A, B, C, X, Y and W (previously W135) 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. Cases may present with atypical symptoms, including gastrointestinal symptoms, which may contribute to delayed diagnosis and could possibly explain high fatality rates. 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 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.
Vaccines that protect against meningococcal disease have been available since the 1970s but none protect against all the groups that cause disease. The current vaccines available in NZ protect against disease by groups A, C, W and Y.
The group B meningococcus is the most effective at evading the immune system, which makes it difficult to create a group B vaccine. New Zealand, Norway and Cuba have used specially manufactured vaccines against a single strain of meningococcal group B to reduce epidemic levels of disease in those countries. NZ used a single strain meningococcal B vaccine (MeNZBTM) between 2004 and 2008 to control an epidemic which has now waned. This vaccine is no longer available and there are currently no meningococcal group B vaccines available in New Zealand. However, a multiple strain meningococcal vaccine that includes group B vaccine has been added to the immunisation schedule in the UK and is approved in Australia.
How you get it
Meningococcal bacteria are commonly carried in the nose and throat, and do not usually cause disease. The bacteria can be transferred from person to person through contact with saliva, for example through intimate kissing. Saliva on shared drink bottles or pacifiers (dummies) may also have a limited role in passing the bacteria from one person to another. The bacteria may also be shared through droplets of saliva in the air from people coughing, sneezing or laughing.
It is not clear why in some vulnerable people the bacteria pass into their blood and brain to cause meningococcal disease (septicaemia or meningitis).
Initial symptoms are difficult to distinguish between viral or other bacterial infections, such as influenza. The symptoms usually start and progress quickly, often within 24 hours.
Infants may have:
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. Cold extremities and colour changes are early warning signs.
Older children, adolescents and adults may have:
Fever, malaise, nausea, vomiting, muscle aches and pains, drowsiness, headache, dislike of bright light, neck stiffness or have a rash or spots.
About 2/3 of cases will develop a rash that does not blanch (disappear) when pressed on. This type of rash is caused by bleeding under the skin and is a sign of advanced blood infection (septicaemia). About 75% of cases of invasive meningococcal disease have meningitis.
Clinical illness associated with the hypervirulent meningococcal W strain tends to be severe. Cases may present with atypical symptoms, including gastrointestinal symptoms, which may contribute to delayed diagnosis and could possibly explain high fatality rates.
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.
Being exposed to tobacco smoke, living in a crowded household or having another respiratory infection, e.g. influenza, can increase a person’s chances of carrying the bacteria.
Certain groups are also at increased risk of infection: household and other close contacts of someone with the disease (particularly those who have been intimate), infants and children attending early childhood education or day care centres, and adolescents and young people at boarding school, living in hostels and university residences. Also health professionals and microbiology laboratory staff who are likely to be in close contact with patients or samples with meningococcal disease.
Some people with medical conditions that affect their immune system have an increased risk of infection, such as those without a functioning spleen, and those who are immunosuppressed from a disease or treatment of a disease.
Infants, children less than five years of age and adolescents, aged 15-19 years, have an increased risk of meningococcal disease. Māori or Pacific infants and young children have the greatest risk.
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 inflammation)
- 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, about 1 person in 10 will die
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.
Vaccination is recommended, but not funded, for young children and adolescents. Meningococcal vaccines to protect against disease caused by meningococcal groups A, C, Y and W are available in New Zealand. A meningococcal vaccine to protect against group C only is also available. Please refer to the IMAC factsheet on available meningococcal vaccines.
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.
Complications of disease
Responses to meningococcal vaccines
|Responses to conjugate vaccines||
|Responses to polysaccharide vaccine||
As with any medicine, very rarely, severe allergic reactions occur following immunisation
- Baker MF, et al. Household crowding a major risk factor for epidemic meningococcal disease in Auckland children. Pediatr Infect Dis J. 2000;19:983-90.
- Harrison L, et al. Meningococcal capsular group A, C, W, and Y conjugate vaccines. In: Plotkin S, Orenstein W, Offit P, Edwards K, editors. Plotkin's Vaccines. 7th ed. Philadelphia: Elsevier; 2018. p. 619-43.
- Institute of Environmental Science and Research Ltd. New Zealand public health Surveillance report March 2018. Wellington: Institute of Environmental Science and Research Ltd (ESR); 2018.
- Lopez L, Sherwood J. The epidemiology of meningococcal disease in New Zealand 2013. Wellington: Institute of Environmental Science and Research Ltd (ESR); 2014. Report No.: FW14023.
- McCall BJ, et al. Risk factors for invasive meningococcal disease in southern Queensland, 2000–2001. Intern Med J. 2004;34:464-8.
- Ministry of Health. 2012, last update May 2018. Communicable Disease Control Manual 2012. Wellington: Ministry of Health.
- Ministry of Health. Immunisation handbook 2017 2nd edition. Wellington: Ministry of Health; 2017.
- Musher DM. How contagious are common respiratory tract infections? N Engl J Med. 2003;348:1256-66.
- Stephens DS, at al. Epidemic meningitis, meningococcaemia, and Neisseria meningitidis. Lancet. 2007;369:2196-210.