Fatal Cross-Border Plague in Zombo District, Uganda, March 2019

Abstract Background: Plague, which is caused by Yersinia pestis , is a priority zoonotic disease targeted for elimination in Uganda. Untreated bubonic plague, resulting from a flea bite, can develop into pneumonic plague, or pneumonic plague may be transmitted in respiratory droplets from person to person. On 6 March 2019, the Uganda Ministry of Health was notified of a patient in Zombo District with clinical presentation similar to pneumonic plague, and a positive plague rapid diagnostic test (RDT). The patient had family links to the Democratic Republic of Congo (DRC). We determined the scope of the outbreak, determined the mode of transmission, and recommended evidence-based control and prevention measures. Methods: A suspected pneumonic plague case was ≥2 of: cough (bloody or wet), chest pain, difficulty in breathing, or fever in a resident of Zombo District during February 1-March 31, 2019. A confirmed case was a suspected case testing positive for Yersinia pestis by rapid diagnostic test, culture or serology. We actively searched for case-patients, traced contacts and took samples as appropriate. We performed descriptive epidemiology of the outbreak. Results: We identified one suspected and one confirmed pneumonic plague case. On February 26, 2019, a 4-year-old boy was buried in DRC near the Uganda border after reportedly succumbing to a disease consistent with bubonic plague. Case-patient A (35-year-old mother to the boy), fell ill with suspected pneumonic plague while attending to him. She was referred to a health facility in Uganda on February 28 but died on arrival. On March 4, Case-patient B (23-year-old sister to Case-patient A), who attended to Case-patient A, presented with pneumonic plague symptoms to the same Uganda facility and tested plague-positive by RDT, culture, and serological tests. Contacts (n=114) were traced and given antibiotics as prophylaxis; no new cases were reported. Conclusion: This fatal plague outbreak started as bubonic and later manifested as pneumonic. There was cross-border spread from DRC to Uganda with no cross-border efforts at prevention and control. Person-to-person transmission appears to have occurred. The quick and effective response likely minimized spread.