Maybe that Harry has faced worse than Sirius Black before, and say that he has had two close encounters with Lord Voldemort. Make sure to elaborate on why LV is such a terrible person. You can also talk about Hogwarts being unsafe for the first time. And what will protect Hogwarts, and Harry's issues with it.
HIV is often thought of as the most widespread in infection counts of all these and is more widely known than the others in those terms HIV is the answer.
