Health officials have issued an urgent warning about a rapid rise in measles cases across parts of the UK, particularly in south west England: there have been 21 new cases in Bristol alone, making it the worst-affected city. The rise is linked to declining MMR vaccination rates, which have fallen below 90%, below the 95% threshold needed to prevent outbreaks. Nationwide, nearly 3,000 cases have been recorded since January 2024, almost half of them in London. Measles, which causes flu-like symptoms, fever, and a distinctive rash, can lead to life-threatening complications such as meningitis and sepsis. Pregnant women, infants, and immunocompromised individuals are most at risk. Doctors urge vaccination as the most effective protection, with two MMR doses providing 99% immunity. The public is advised to stay vigilant, seek medical advice for symptoms, and avoid schools, workplaces, and gatherings if infected.