Meningococcal disease is caused by the bacterium Neisseria meningitidis. Humans are the only host for these bacteria.
At least 12 groups have been identified, including groups A, B, C, X, Y and W (previously called W-135). The pattern of disease caused by each group varies by time and country or geographical areas. In New Zealand from 2015 to 2017, groups B and C were the most frequent causes of meningococcal disease. However, this has changed since 2018 with an increase in disease caused by groups W or Y. Over 2018–2019, just under half of cases were caused by meningococcal group B, and just under half by groups C, W or Y. Meningococcal group A rarely causes disease in New Zealand.
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. Isolated outbreaks of meningococcal groups A and C have occurred in New Zealand: the last group A outbreak was in 1985/86 in Auckland. Northland experienced an outbreak of meningococcal group C disease during 2012. Then in 2018, Northland experienced a disproportionately high number of meningococcal diseases cases (7.4 cases per 100,000 people) compared with New Zealand overall (2.5 cases per 100,000). Group W was the predominant cause of meningococcal disease in Northland in 2018.
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.
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.
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.
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.
If meningococcal bacteria pass into the blood, the disease usually progresses very quickly. A person with meningococcal disease may develop:
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.
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. A fact sheet about meningococcal vaccines can be downloaded from the Resources section on this page.