Outbreaks of bacterial meningococcal disease in England and recent cases in students in New Zealand have raised awareness of this serious and life-threatening disease.

The disease is caused by the bacterium Neisseria meningitidis and presents as meningitis or blood poisoning (septicaemia).

Meningitis is an inflammation of the membranes that cover the brain and spinal cord (meninges), while septicaemia affects the whole body through the presence of bacteria in the blood stream.

Both can be also be caused by other infectious agents, but bacterial meningococcal disease is the most severe form.

Infants, children and young adults are at higher risk. While the disease is largely preventable through vaccination, only one vaccine is currently on the national immunisation schedule in Aotearoa New Zealand.

As part of ongoing research to explain the recent cases, we compared the meningococcal strains involved in both countries and explored the significance of people who carry the bacterium but don’t develop symptoms or disease.

There are several strains of Neisseria meningitidis and most belong to six groups (named A, B, C, W, X and Y). All have an extraordinary ability to swap genetic material between them and switch genes on and off through a process known as phase variation.

This can change the surface of the bacterium, enabling it to escape the body’s immune........

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