The bacteria only rarely give rise to meningococcal disease, but when they do infection spreads rapidly and is fatal in about 10% of cases. If disease is diagnosed early and treated promptly most people make a full recovery.
About 1 in 8 people who recover experience some long term effects. These can include headaches, stiffness in the joints, epileptic fits, deafness and learning difficulties.
More top news
Once a year W11 comes alive with the colour of carnival. Everything you need to know about getting around and what to see in Notting Hill.
People should only be allowed to move freely within the EU if they have a job waiting for them, the Home Secretary has said.
A 62-year-old woman has been found alive more than a week after she vanished while on a hiking trip.