As I walk into many, many of homes where people have just moved out and I realize one thing; some people get sick simply by living in filth. I believe it's like anything else in life. Someone that eats a greasy burger once is not gonna gain any weight. But a person that eats a greasy burger once a day for a year sure will. People that have dirty home often let it progress little by little. As a house cleaner in Santa Maria, a small town out in California, I see a lot of this.