everyday! my wife is an epidemiologist. She studies diseases in populations like Tuberculosis (TB), HIV, obesity and the most infectious bacteria known – Q-fever (http://en.wikipedia.org/wiki/Q_fever). She worked on an outbreak of Q-fever that started in an abattoir (where they slaughter animals for meat) in scotland some years ago. A few people got very sick.
Yes, though not as often as Andrew! I have met a few epidemiologists on training courses. They have a very interesting and important job. While some scientists work in the lab to understand how diseases work and how we can treat them, epidemiologists work with records and statistics to calculate how often a disease occurs and what its effects are. Their work is extremely important as it helps us to focus our research on where it is needed the most – for example, if a lot more people are dying of flu this year and heart disease is much less of a problem, then more funding can go to flu research and less to heart disease.