Pneumonic plague is caused by the Yersinia pestis bacteria, usually found in small mammals and their fleas.

A deadly form of plague has broken out on Uganda’s border with the Democratic Republic of the Congo (DRC) and several people are thought to have died of the disease, the World Health Organization said earlier this week.

The agency praised Ugandan health workers for vigilance and prompt action in spotting a suspected outbreak of pneumonic plague, which the WHO says is usually fatal unless detected early and treated with antibiotics.

Uganda’s health ministry reported two probable cases of the illness in Zombo district on March 5 after a 35-year-old woman died and her 23-year-old cousin reported similar symptoms, the WHO said in a report.

Further investigation revealed the dead woman had lived in Atungulei village in the DRC’s Ituri province, and her 4-year-old child had died days beforehand. Seeing that she was ill at her child’s burial, her relatives took her to Uganda for treatment.

The cousin’s symptoms raised suspicions of plague and a preliminary rapid diagnostic test was positive for the disease. Results on additional specimens sent to Uganda’s Plague Laboratory in Arua were pending. The patient was steadily improving, the WHO report said.

Some 55 people, including 11 health workers and people who took part in the dead woman’s funeral, had been identified as high-risk contacts and were being monitored.

Three other people reportedly died of similar symptoms in the DRC, the WHO said, and local authorities were investigating.

Felix Ochom, an epidemiologist with WHO, told Al Jazeera that while the outbreak is cause for concern, it is under control.

“From the Ugandan side, we are working closely with the Ministry of Health and the district health authorities in Zombo district,” he said, speaking from Kampala.

“It is treatable and the suspected case we identified in Zombo district is undergoing treatment and improving quite steadily.”

Situation ‘stable’ on the Ugandan side

Plague is endemic in the DRC, Madagascar and Peru, according to the WHO.

Congolese health authorities are already fighting a major outbreak of Ebola further south in Ituri and North Kivu provinces.

Ochom said that conflict and the outbreak of Ebola on the DRC side “would further complicate an already difficult situation”, in contrast, the situation on the Ugandan side is “quite stable”.

Pneumonic plague is caused by the Yersinia pestis bacteria, usually found in small mammals and their fleas. Humans can be infected through flea bites, unprotected contact with bodily fluids or contaminated materials, and the inhalation of droplets or small particles from a patient with pneumonic plague.