Scientists have finally figured out why the meningitis B outbreak in Kent earlier this year was the UK's worst ever, and the answer is basically bacterial plagiarism. More than 20 young people, mostly students, were infected in the March outbreak linked to a Canterbury nightclub. All needed hospital treatment, nine ended up in intensive care, and two died.

Experts at the UK Health Security Agency (UKHSA) and the University of Oxford, who examined the bacterium's DNA, say it picked up genetic material from other bugs naturally found in some people's throats. This little exchange created a new strain that then spread between clubbers and caused severe illness. Because nothing says "great night out" like a side of horizontal gene transfer.

Experts stress the meningitis vaccine currently being offered to more than a million young people starting university protects against it. So that's reassuring.

"This investigation shows just how quickly and dramatically these bacteria can change," says Dr Charlene Rodrigues, consultant in Pathogen Genomics at UKHSA. "The fact this outbreak variant was able to spread to so many young people was due to the social environment, a place where lots of close social mixing takes place."

Speaking exclusively to the BBC, she said bacteria are known to undergo changes like this, known as horizontal gene transfer. Such changes can make infections more severe and may mean they get past the immune system because people haven't encountered them before. These events, while rare and unpredictable, could happen again, so experts "should not take their eye off the ball," she added.

Scientists say the speed and severity of the Kent outbreak was very unusual. It was described as "unprecedented" and "explosive" at the time, with so many infections happening in one place over a very short period. Two people died: a 21-year-old University of Kent student and Juliette Kenny, a sixth-form pupil at Queen Elizabeth's Grammar School in Faversham.

The outbreak is thought to have started in a nightclub called Club Chemistry in the city centre, which was popular with university students. It's likely one person brought the infection in with them, and then it spread that evening. Meningitis is passed through close contact, including kissing and sharing drinks or vapes.

Dr Rodrigues suspects the very same genetic changes that made the strain so dangerous may also explain why the outbreak was short-lived and did not continue to spread. People were generally too sick to be silent carriers who can pass it on unknowingly to others. So, in a twist, the bacteria's own aggression may have been its downfall.

Following the Kent outbreak, a one-off menB vaccination programme was launched to protect young people heading to university this autumn. In July, the Joint Committee on Vaccination and Immunisation (JCVI) also recommended that teenagers should be offered the jab on the NHS around the age of 15, with catch-up programmes for those who would otherwise miss out.