Tularemia cases rise nearly 60% in US
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Key takeaways:
- Nearly 2,500 cases of tularemia were reported in the U.S. between 2011 and 2022.
- Cases of the disease — also called rabbit fever — were most common in children and older adults.
Cases of tularemia — a relatively rare zoonotic disease — increased by nearly 60% in the United States from 2011 to 2022 compared with the preceding decade, according to CDC researchers.
“This CDC report shows cases of tularemia are becoming more common in the United States,” Kiersten Kugeler, PhD, an epidemiologist in the CDC’s Division of Vector-Borne Diseases, told Healio. “The causes for the increase in reported cases are not clear and probably reflect several factors, including more people being infected and better methods for detecting cases.”
Tularemia, also known as rabbit fever, is caused by the bacterium Francisella tularensis, which the U.S. considers a “tier-1 select agent” because of its potential to be weaponized, Kugeler and colleagues noted.
The infection most often occurs in rabbits, hares and rodents — including rats. Humans can be infected through the bite of a tick, deer fly or other insect or from exposure to infected animals, inhalation of contaminated aerosols, or by drinking contaminated water, according to the CDC.
Kugeler and colleagues analyzed data on all tularemia cases reported to the CDC through the National Notifiable Diseases Surveillance System between 2011 and 2022.
Overall, a total of 2,462 tularemia cases were reported during the 12-year time period — 40% of them confirmed cases and 60% probable cases. According to the study, a mean of 205 cases was reported during each of the 12 years (ranging from 149 to 314 cases per year). During the study period, 50% of all cases were reported in just four states: Arkansas (18%), Kansas (11%), Missouri (11%) and Oklahoma (10%)
The overall average annual incidence was 0.064 cases per 100,000 population — a 56% increase in average annual incidence over the 0.041 cases per 100,000 population reported between 2001 and 2010, according to the researchers, who attributed the increase to an increased reporting of probable cases after laboratory criteria were updated in 2017 to include PCR test results, as well the potential for an actual increase in human infections and improved laboratory case detection.
Among the cases, 63% were male, and the incidence was highest among children aged 5 to 9 years (0.083 per 100,000 population) and older adult males aged 65 to 84 years (0.133 to 0.161 per 100,000 population).
Kugeler said that although the signs and symptoms of tularemia are “broad and often nonspecific,” health care providers should consider the infection in patients with comparable symptoms who have had possible exposure to F. tularensis.
“The findings in this report highlight the need for tailored prevention education given the myriad potential exposures to F. tularensis in the environment,” Kugeler said. “Increasing incidence underscores the needs for clinical education regarding diverse clinical manifestations of tularemia, options for laboratory testing and important and early and appropriate treatment.”
References:
- CDC. Tularemia: About tularemia. https://www.cdc.gov/tularemia/about/index.html. Updated May 15, 2024. Accessed Jan. 3, 2025.
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