Smallpox is a contagious disease caused by a virus. Smallpox virus has been eradicated worldwide through successful vaccination and treatment programs, and now exists only as a stored virus in a few research centers. Symptoms include a severe rash (which leaves scars), fever, headache, vomiting and diarrhea.
Update Date 6/23/2011
Updated by: Jatin M. Vyas, MD, PhD, Assistant Professor in Medicine, Harvard Medical School; Assistant in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.