Legionnaires' disease and associated comorbid conditions as causes of death in the U.S., 2000-2010.

Objective: Recent U.S. outbreaks of Legionnaires' disease (LD) underscore the virulent nature of this infectious pneumonia. To date, only a paucity of literature has described the mortality burden of LD. This study updates LD mortality using U.S. multiple-cause-of-death data from 2000-2010.

Methods: We calculated crude and age-adjusted rates for LD mortality for age, sex, race, state, Census region, and year. We conducted Poisson regression to assess seasonal and temporal trends. We generated matched odds ratios (MORs) to describe the association between LD-related deaths and other comorbid conditions listed on the death certificates.

Results: We identified a total of 1,171 LD-related deaths during 2000-2010. The age-adjusted mortality rate remained relatively static from 2000 (0.038 per 100,000 population, 95% confidence interval [CI] 0.031, 0.046) to 2010 (0.040 per 100,000 population, 95% CI 0.033, 0.047). The absolute number increased from 107 to 135 deaths during this period, with adults ≥45 years of age having the highest caseload. Overall, LD mortality rates were 2.2 times higher in men than in women. White people accounted for nearly 83.3% of all LD-related deaths, but the age-adjusted mortality rates for black and white people were similar. Comorbid conditions such as leukemia (MOR=4.8, 95% CI 3.5, 6.6) and rheumatoid arthritis (MOR=5.6, 95% CI 3.3, 9.4) were associated with LD diagnosis on death certificates.

Conclusion: Comorbid conditions that could lead to an immunocompromised state were associated with fatal LD on U.S. death certificates. Characterization of LD mortality burden and related comorbidities has practice implications for clinical medicine and public health surveillance.