Diagnosing smallpox: would you know it if you saw it?

The intentional release of anthrax in the United States in 2001 and other recent acts of terrorism have highlighted the possibility of intentional release of smallpox by terrorists. Little is known about physicians' ability to diagnose smallpox, especially in the critical first days, when the potential for rapid control of transmission is greatest. During December 2002 and January 2003, primary care and emergency physicians at a large urban academic medical center were surveyed regarding the diagnosis and management of patients who present with vesicular rash illness. In addition to demographic and training-related questions, the questionnaire included items about perceived comfort in diagnosing and evaluating rashes, knowledge of the key differential diagnostic characteristics of chickenpox and smallpox, and the diagnostic interpretation of color photographs of patients with smallpox or chickenpox. Responses were summarized as a perceived comfort score, a differential diagnosis score, and a picture score. Of 266 eligible physicians, 178 (67%) responded. Of these, 95% thought clinicians need more education about bioterrorism; only 17% reported comfort in diagnosing smallpox. Although most physicians recognized pictures of smallpox and chickenpox, only 36% correctly answered 3 of 4 questions regarding differential diagnosis, an important aspect of identifying cases early. Those who were comfortable diagnosing rash illnesses had higher differential diagnosis scores. Strategies for bioterrorism-related training could take advantage of physicians' awareness of their own knowledge deficits.