Lupus is a chronic disease of the immune system that is not contagious. It can be triggered by various environmental factors, and there seems to be a genetic predisposition to the disease, but as the Lupus Foundation of America explains, it cannot be transmitted from person to person even with close contact.
Lupus develops unpredictably in each patient and can be very difficult to diagnose. No known pathogen is responsible for the disease, and the only sense in which it "spreads" is vertically from parents to children through genetic inheritance. Many people with a family history of lupus never develop symptoms of the disorder, while others suffer outbreaks that range from mild to life-threatening, notes the Lupus Foundation of America.
According to Mayo Clinic, lupus outbreaks can be triggered by exposure to sunlight, inflammation that triggers an exaggerated immune response and certain medications. Medication likely to trigger lupus includes various anti-seizure drugs, blood pressure treatments and some antibiotics. Often, patients who show symptoms after beginning a course of these medications report that most or all of their symptoms go away after they stop taking the drugs. Despite the research done into lupus, much of the time, the environmental trigger that causes the disease to flare up remains unknown.