Sophia Mulei, Daniel Orit, Mary J Choi, Shannon Whitmer, Katrin S Sadigh, Jimmy Baluku, Kami Smith, Alison Todres, Calvin R Torach, Benigna Namara, Michael Nanjubu, Simon P Lubega, Abdullah Baguma, Emmanuel Ejoku, Jens H Kuhn, Shuiqing Yu, Sandor Karpathy, Ariel Christiansen, Terry Fei Fan Ng, James Sejvar, Trevor Shoemaker, Joel M Montgomery, Julius Lutwama, Daniel Kadobera, Christopher Kiyita, Henry Mwebesa, Luke Nyakarahuka, Stephen Balinandi, John D Klena
In September 2023, a cluster of unexplained illness in women affecting their ability to stand/walk was reported at Bundibugyo Hospital, Uganda. Field investigations were conducted to verify reports, conduct active case finding, and identify potential causes using a hypothesis-generating questionnaire, a neurological examination tool, and a standardized laboratory panel. As of January 31, 2025, 136 patients were identified; all were female. Among 108 with age data, the median age was 18 years old, and all but one lived in Bundibugyo District. All reported bilateral lower-extremity tremors interfering with their ability to stand/walk that resolved when sitting or lying down. Of 75 women evaluated, 33 (44%) were acutely symptomatic at assessment. Tremors lasted between 4 days and 3 months. Of 90 women who provided symptom recurrence information, 20 (22%) reported recurrent episodes. No shared environmental exposures of concern were identified among 76 patients with data. Although limited female-specific exposures were noted, no known toxins were identified among patients. Blood specimens were submitted for laboratory testing, and 24 of 93 (26%) tested positive for Plasmodium. One of 34 (3%) tested positive for Shigella spp. Three of 87 (3%) were positive for Ekpoma virus 2 (EKV2), and 41 of 80 (51%) were anti-EKV2 IgG positive. Metagenomic sequencing confirmed two of the EKV2 cases and identified rickettsiae-specific reads in one individual. It is still unknown whether the cause is an infectious agent or an environmental toxin. This outbreak highlights the importance of strong field epidemiology and laboratory capacity in investigating emerging neurological syndromes.