Anthrax outbreak linked to handling and consumption of infected meat, Sembabule District, Uganda, October–December 2024

Introduction: Despite multiple outbreaks annually, Uganda still lacks a national anthrax control program. While the surrounding districts of Gomba, Kazo, and Kiruhura had experienced anthrax outbreaks previously, Sembabule had not documented any. On December 4, 2024, four meat dealers in Sembabule District developed skin lesions and were confirmed to have anthrax. We conducted an investigation to assess the magnitude of the outbreak, identify risk factors, and recommend control measures. Methods: Suspected cutaneous anthrax was characterised by the onset of skin lesions (papule, vesicle, or eschar) in a resident of Sembabule District from October to December 2024. Suspected gastrointestinal anthrax was the acute-onset abdominal pain with diarrhea, vomiting, pharyngitis, or oropharyngeal lesions. Suspected animal anthrax was the cause of the sudden death of a domestic herbivore with bloody discharge from natural orifices. Laboratory samples were collected from a subset of suspected cases to confirm the outbreak etiology. A confirmed case was any suspected case with a clinical sample positive for Bacillus anthracis by polymerase chain reaction (PCR). We identified human cases by reviewing medical records and community case search. We explored risk factors through interviews with farmers and health workers. We compared exposures among 40 human cases and 158 neighbourhood controls to identify risk factors for anthrax. Results: Among 45 human cases (36 suspected, 9 confirmed), two (4.4%) died. Thirty-four (76%) had cutaneous anthrax, five (11%) gastrointestinal anthrax, and six (13%) had both forms. Males were more affected than females (24 vs 4/100,000). Among 25 animal cases, two (8.0%) were confirmed. Infected cattle were introduced into Sembabule District from Kazo District in October 2024 and mixed with herds in Sembabule. When these animals died, meat dealers distributed the meat, selling it at one-third the normal price. Butchering (OR=13.3, 95%CI:5.8-30.7), carrying (OR=6.3, 95%CI:2.8-13.8), and eating meat from dead animals (OR=8.7, 95%CI:3.8-20) significantly increased infection risk. Conclusion: The anthrax outbreak in Sembabule District was triggered by the introduction of sick cattle and spread by butchery and distribution of infected meat. Given the frequent outbreaks in this region of Uganda, a One Health approach, including livestock vaccination and sustained risk communication to change community practices, may be needed to facilitate anthrax control