Question: What is the most infectious disease you've come across?

Leo Beacroft answered on 8 Jun 2018:

Measles is one of the most infectious diseases that’s still around today. By “most infectious” I mean that it spreads very quickly. If you had a population where nobody was immune and one person had measles, then that person would infect about 15 people, then those 15 people would each infect around 15 other people and so on. Eventually the spread would slow down, but it would probably lead to most of the population getting infected. Luckily this doesn’t happen in the UK, as we have a vaccine for measles that most people have when they’re very young, but there are still some cases among people who don’t get vaccinated or people with weak immune systems.
Thanks for your question, let me know if there’s anything else you want to know!