But they're spreading extremely fast and one of them, in Ventura County, northwest of Los Angeles, is almost three times larger than the worst fire we reported on in October.
But what alarmed medical officials a couple of weeks ago is that the disease had spread to a city named Mbandaka, where more than a million people live and there were concerns that it could spread quickly there.
The higher the rating, the more dangerous the conditions are likely to be, and at higher ratings any fire that starts will be likely to be fast-moving and difficult to control.