Uganda’s 2006 Plague Outbreak

People are sometimes surprised to learn that the plague still exists today. They ask me why they  have never heard about it in the news. Well, it is occasionally in the news for a day and then we go on to the next crisis. Today plague outbreaks occur in parts of the world that don’t get  good or sustained news coverage.

About 90% of plague cases reported to the World Health Organization today  come from Africa.  Uganda experiences about 200-400 cases per year with an case fatality rate of 30%. This cluster of 127 cases occurred between July and December of 2006 in the Arua and Nebbi districts of northwestern Uganda. Some of the initial patients did not seek medical care because they believed the illness and deaths were due to a local feud. Only when people not associated with the feud died did they begin to seek medical treatment at a local clinic. Diagnosis of plague by symptoms can be difficult enough without patients attributing illness to supernatural causes.  Cases were spread over the region with four villages producing ten or more cases and nine villages producing at least two cases.

Due to a lack of clinical laboratories in the region, most patients had to be diagnosed by clinical symptoms: a sudden fever, chills, headache, fatigue, and a painful, swollen lymph node(s) in bubonic plague or a bloody cough in pneumonic plague. Development of the plague rapid diagnostic test was done for areas like this region of Uganda where lab facilities are sparse. These newer tests appear not to have been available for this outbreak. Of the 127 recognized patients, 88% had bubonic plague and 12% had pneumonic plague. Once villagers began seeking treatment they were given antibiotics and most recovered. The overall fatality rate for this outbreak was 22%, although 11 of 12 cases of pneumonic plague died.

Pneumonic cases clustered in families. In one documented cluster, a 10 year old boy initially developed bubonic plague with a bubo on his neck. He developed a bloody cough and soon died, to be followed by the deaths of mother, grandmother and aunt. Two others from this village also died of pneumonic plague. In another cluster related to this outbreak (but excluded from study data) a 15 year old girl contracted pneumonic plague while visiting relatives in the Nebbi region and returned to her home district of Masindi, starting an outbreak the killed seven.

Interviews were conducted with 39 recovered patients from two villages. Dead rats reported in or around the homes of 59% of the interviewed patients, including some who buried the dead rats near their homes. Four of eight dead rats collected by the investigative team from these two villages tested positive for Yersinia pestis. Trapped live rats were found to have an average of two fleas per rat; more than one flea per rat is associated with increased risk of plague transmission.

While this outbreak may seem small compared to medieval plagues, this is the spark from which a great epidemic can grow. Antibiotics and knowledge of the importance of rodents in transmission prevent these epidemics from growing. The people in these villages didn’t associate rat deaths with their illness and neither did medieval people. Plague is still very much on the radar screen of ministries of health throughout Africa and around the world.

Centers for Disease Control and Prevention (CDC) (2009). Bubonic and pneumonic plague – Uganda, 2006. MMWR. Morbidity and mortality weekly report, 58 (28), 778-81 PMID: 19629028