BACKGROUND: Tularemia is a zoonosis caused by the bacterium Francisella tularensis, a tier-1 agent with multiple modes of transmission and potential for use as a bioweapon. Clinical illness varies with route of infection and ranges from mild to life-threatening.
METHODS: In addition to core variables transmitted via the National Notifiable Diseases Surveillance System (NNDSS), states voluntarily provide supplemental information on symptoms, likely exposures, and severity of illness for tularemia cases.
RESULTS: We reviewed supplemental information for 593 tularemia cases from 40 states during 2006-2015, accounting for 37% of total cases reported during this period. Most cases with supplemental information were laboratory confirmed (419, 71%) and occurred among males (389, 66%), similar to cases reported to NNDSS. Median age among supplemental records was slightly higher than in NNDSS (51 years vs. 46 years). Records for 548 cases (92%) had a defined primary clinical presentation; the most common was ulceroglandular (302, 55%) followed by pneumonic (83, 15%), glandular (81, 15%), and typhoidal (61, 11%); oculoglandular and oropharyngeal presentations were rare. Most patients reported general symptoms of fever or chills (516, 89%); fewer reported gastrointestinal symptoms (203, 35%). Subtype was available for 246 cases; 63% of these were type A and 37% were type B. Of 534 cases with exposure information, 47% reported a tick or deerfly bite, 43% participated in aerosol-generating activities such as mowing or landscaping, 23% reported contact with a sick or dead animal, and 11% experienced an animal bite or scratch. The proportion of cases lacking identifiable exposure did not differ by clinical presentation. Among ulceroglandular cases, 54% had documented arthropod exposure, although direct animal contact was also common (40%). Aerosol-generating activities were reported for a majority of patients with pneumonic (82%) and typhoidal (66%) presentations. Overall, 59% of patients were hospitalized; hospitalization occurred most frequently among those with pneumonic tularemia (67, 83%) but was also common among persons with typhoidal (41, 68%), ulceroglandular (153, 52%), and glandular (34, 43%) manifestations. Frequency of hospitalization was similar between infecting subtypes. Illness outcome was available for 477 cases (80%); 61% recovered without complications, 35% recovered with complications, and 4% died.
CONCLUSIONS: Supplemental surveillance data provide important insights into the epidemiology of tularemia, including typical modes of transmission. The ability to detect unusual patterns and potential intentional events is linked to the robustness of baseline data and dependent on data sharing. Informatics improvements should streamline sharing of detailed case information.