Q Fever Is Underestimated in the United States: A Comparison of Fatal Q Fever Cases from Two National Reporting Systems

Two national surveillance systems capturing reports of fatal Q fever were compared with obtained estimates of Q fever underreporting in the United States using capture–recapture methods. During 2000–2011, a total of 33 unique fatal Q fever cases were reported through case report forms submitted to the Centers for Disease Control and Prevention and through U.S. death certificate data. A single case matched between both data sets, yielding an estimated 129 fatal cases (95% confidence interval [CI] = 62–1,250) during 2000–2011. Fatal cases of Q fever were underreported through case report forms by an estimated factor of 14 and through death certificates by an estimated factor of 5.2.