Reading an English book

I bought an English book last weekend and started reading. The title of the book is How to Prevent the Next Pandemic, written by Bill Gates. I have known him as a programmer and a founder of the well-known tech company, Microsoft. I think I have heard that he is involved with health care now but I did not know clearly how he associates with the activity. I have not finished reading it yet but the content is quite interesting for me. He precisely describes how he acted in the pandemic. I have never heard the definition of outbreak, pandemic and epidemic. Also, it is inevitable to avoid outbreak of diseases but it can be prevented from wide-spread with human efforts. I will keep reading it to learn new things and improve my English.