Rising Tularemia Cases Demand Action: CDC Highlights Advances in Diagnostics and Calls for Targeted Efforts to Protect Vulnerable Communities.
Report: Tularemia — United States, 2011-2022. Image credit: Kateryna Kon/Shutterstock
In a recent study published in the journal Weekly Morbidity and Mortality Reportscientists from the U.S. Centers for Disease Control and Prevention (CDC) examined the demographic patterns, geographic distribution and incidence trends of tularemia, a rare bacterial disease caused by Francisella tularensis. This disease can infect humans through various routes, such as insect bites, contaminated food or water, and inhalation.
Background
Tularemia is a zoonotic disease caused by the bacteria Francisella tularensis. Humans can contract the disease through contact with infected animals, insect bites, inhaling contaminated particles, or drinking polluted water. Symptoms vary widely, including fever, localized infections, or severe breathing problems.
Although the disease can be treated with antibiotics, tularemia can cause significant health problems, especially if diagnosed late. Historically, the disease has been reported in most U.S. states, with some regions and demographic groups experiencing higher incidence rates. Notably, environmental and occupational exposures, as well as proximity to wildlife, contribute to these trends. Additionally, populations in central states and American Indian or Alaska Native communities often face a disproportionate burden of disease.
Although surveillance efforts and laboratory advances have improved case detection in recent decades, the disease remains underreported and poorly understood. The lack of a preventative vaccine and the various clinical presentations further highlight the importance of enhanced public health measures and medical education to reduce its impact on vulnerable populations.
Reported tularemia cases, by county of residence – United States, 2011-2022
About the study
The current study used tularemia surveillance data reported to the CDC from 2011 to 2022. Cases were classified into confirmed or probable categories based on clinical and laboratory criteria. Confirmed cases were determined based on isolation of F. tularensis or antibody titers showing at least a fourfold change between acute and convalescent stage serum samples.
Additionally, probable cases were identified by a single high antibody titer or detection of the bacteria by fluorescent testing or polymerase chain reaction (PCR). The inclusion of PCR methods in 2017 marked a significant advancement in diagnostic criteria. Researchers analyzed data on annual incidence rates by demographic groups, geographic locations and case classifications.
Additionally, population estimates from the US Census Bureau were used to calculate rates per 100,000 individuals. The study also examined temporal trends in tularemia cases and assessed the impact of changes in surveillance criteria and advances in laboratory diagnosis over the years.
Geographic distribution analysis included county-level mapping, while demographic data focused on age, gender, race, and ethnicity. This comprehensive analysis identified patterns and disparities in disease incidence. Differences in case detection methods, state reporting practices, and laboratory technologies were also considered to contextualize observed trends.
The researchers also discussed some of the study’s limitations, including potential underreporting, variability in state-level surveillance, and the impact of external factors such as the disease 2019 (COVID-19) pandemic. to coronavirus on data collection. These factors highlight the need for consistent and robust surveillance practices across states. The findings were intended to inform public health strategies to reduce the incidence of tularemia and improve diagnostic practices. The investigation complied with ethical standards and federal laws.
Main findings
The study found that the incidence of tularemia in the United States increased by 56% between 2011 and 2022 compared to the previous decade. A total of 2,462 cases were reported during this period, with 40% classified as confirmed and 60% as probable. The increase in probable cases is partly attributed to advances in diagnostic methods, such as the move to enzyme-linked immunosorbent assays (ELISAs), which are more sensitive but less specific than earlier agglutination tests.
Annual incidence rates ranged from 0.041 to 0.064 per 100,000 population, with notable geographic and demographic disparities. Four central states – Arkansas, Missouri, Kansas and Oklahoma – accounted for half of all cases, indicating a concentration of infections in these regions. Children aged 5 to 9 years and men aged 65 to 84 years had the highest age-specific incidence rates.
American Indian or Alaska Native populations experienced rates approximately five times higher than white populations, indicating significant health disparities. Sociocultural and occupational activities, as well as the concentration of Native American reservations in the central states, likely contribute to this increased risk. Additionally, seasonal trends showed that most cases occurred between May and September, likely reflecting increased exposure to vectors during warmer months.
Additionally, temporal analysis found that probable cases consistently outnumbered confirmed cases since 2015, with divergence beginning after the 2017 expansion of laboratory criteria, including PCR detection. Although improved detection methods and increased reporting have likely contributed to the increase in incidence, researchers believe other factors, such as environmental or behavioral changes, may also play a role. role.
The study highlighted the need for targeted prevention strategies for at-risk populations and regions. The findings also highlighted the importance of training healthcare providers to improve early diagnosis and effective treatment, particularly for providers serving tribal populations with limited access to specialized medical resources.
Conclusions
The study called attention to a growing trend in tularemia incidence in the United States, driven by better detection methods and an increase in case reports. The geographic and demographic disparities observed in the study highlighted vulnerable populations requiring targeted prevention and education efforts.
Addressing these disparities through tailored public health initiatives, targeted clinical education, and improved laboratory testing practices can reduce health inequities and improve outcomes. CDC researchers believe that addressing these disparities through public health initiatives, early diagnosis, and prompt treatment can lessen the impact of the disease, reduce health inequities, and improve outcomes for those most affected. at risk.
