Active surveillance for human plague in Northwestern Uganda, 2008-2014

Abstract

Background: Plague is a life-threatening flea-borne zoonosis caused by Yersinia pestis. Over 95% of cases worldwide are reported from rural Africa. In Uganda, the active plague foci remains in West Nile region bordering Democratic Republic of Congo. To better define the epidemiology, clinical features, and outcome of human plague in Uganda, several surveillance strategies and networks used have significantly reduced morbidity and mortality. Methods & Materials: Active surveillance, coupled with central laboratory support, was established in 10 clinics and 2 hospitals in the endemic West Nile region. Community awareness was enhanced though training of Village Health Team workers and a small number of traditional healers. For surveillance purposes, a suspect plague case was defined as rapid onset of fever and painful lymphadenopathy or hemoptysis. A confirmed case was defined as a suspect case with isolation of Y. pestis from a clinical specimen (blood, bubo aspirate, or sputum) confirmed by phage lysis, or a 4-fold increase in anti-F1 antibody titers. A probable case was defined as a suspect case epidemiological linked to a laboratory-confirmed case. Results: A total of 256 cases were identified during January 2008 – March 2014, including 75 laboratory confirmed and 25 probable cases. The number of cases per full year ranged from a high of 153 in 2008 to a low of 6 in 2014. Median patient age was 11 years (range <1-70 yrs); 53% were female. Overall, 217 patients had bubonic, 20 septicemic, and 18 pneumonic forms of plague. Among 254 patients with a documented outcome, 26% (26/100) with confirmed or probable plague died, as compared with 8% (12/154) of those with suspect plague. Mortality among patients with pneumonic plague was 44% (8/18) overall, and 55% (5/9) for those with confirmed pneumonic plague. Antimicrobials used for treatment included doxycycline, gentamycin, chloramphenicol, co-trimoxazole, and ciprofloxacin. Forty-nine (19.6%) cases were outbreak-related. Conclusion: Plague remains a public health concern in the West Nile region of Uganda. Although most cases are bubonic and sporadic, small outbreak of pneumonic plague with person-to-person transmission do occur, with the potential for larger outbreaks. Mechanisms to enhance prompt referral, rapid diagnosis, and effective antimicrobial treatment are needed to reduce mortality.