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
Prime Minister insists the UK will maintain a strong relationship with Europe especially on trade and security, even after it leaves the EU.
Cloudy, with outbreaks of rain spreading northeast across the UK, however northern Scotland remaining largely dry until later.
The five-year-old was bitten on the face and had to undergo surgery to her eyelid after the dog attacked her at an event in West Yorkshire.