dr. anthony facci. and the author of the book, why we're at risk. explain some terms, sanjay, there's outbreak, epidemic, pandemic, endemic. >> outbreak is usually when you see some sort of eruption of an infection that you wouldn't otherwise expect to see. so even if it's a single case of something that's brand-new, that could be an outbreak. epidemic is when something starts to spread rapidly among the population, pandemic is when it's spreading around the world. endemic is when it becomes sort of entrenched in a particular place, malaria for example, that started off in these first sort of stages but is now endemic within certain parts of africa. >> just in terms of risk, you say you can't prevent outbreaks, you can't prevent the emergence of a new infectious agent, but you can prevent how it spreads? >> that's the whole point, microbes merge and re-emerge, there's nothing you can do about it, but you can prevent an outbreak from becoming a pandemic or an epidemic, with vaccine development, you can plenty that spread. people think, well, prevent