The usual type of virus, which runs outside of a supporting program, is called a system virus. A Windows system virus cannot become a Macintosh system virus. When the media deal with viruses, they are generally talking about Windows system viruses. It is estimated there are somewhere between 2,000 and 12,000 Windows system viruses. When reporters see numbers like this, they see a big problem.
Big problems lead to flashy headlines.
On the other hand, the estimates for the number of viable Macintosh viruses range from 20 to 50, and many of those won't work under Mac OS 8. So, by this simple estimate, the problem appears a hundred times worse under Windows. Of course, this feeling of superiority you get by knowing your Mac has far less chance of being trashed by a virus would fade quickly, if it did get trashed. The truth is that most viruses are fairly benign and won't trash your system. Problems generally appear because of unintended side-effects.