Stopping Imported Pneumonic Plague in Uganda, 2019

This page summarizes a report in CDC's MMWR by the Uganda Virus Research Institute, Uganda's Ministry of Health and CDC, on events in February and March 2019.

Plague, an acute zoonosis, is caused by Yersinia pestis. It is endemic in the West Nile region of northwestern Uganda and in neighboring northeastern Democratic Republic of the Congo (DRC). It takes several clinical forms. Pneumonic plague is rare, kills quickly, and spreads from person to person through respiratory droplets.

In early 2019 it crossed the border, and Uganda stopped it after a single transmission.

Two sisters

Patient A, a 35-year-old Ugandan woman, lived in DRC about 5 km from the Ugandan border.

• February 27. Relatives from Uganda crossed into DRC for the funeral of her 4-year-old child and found her severely ill. They took her to her family's ancestral village in Zombo District, West Nile, where she had chest pain and coughed up blood at least once.
• February 28. She was admitted to a nearby clinic around midday and died a few hours later. No samples were taken. Burial preparations in the village began that day and ended with her burial on March 2.
• Her husband in DRC reportedly died of a sudden illness at about the same time, and others in her family there were ill, some with "fever and swellings."

Meanwhile, a local government office in Uganda received an alert from a private clinic in DRC about possible plague in a village near the border, the village patient A had come from. The plague program of the West Nile-based Uganda Virus Research Institute (UVRI) and local health officials began plague education and risk communication at clinics and among villagers while the burial went ahead.

Patient B, her 23-year-old sister, had not gone to DRC. She reached the village on the morning of February 28 and cared for patient A that morning: she wiped around her mouth by hand, fed her, took her to the clinic by motorbike and stayed with her there. She took no part in carrying the body home or preparing it for burial.

• March 3. Patient B developed a fever.
• March 4. At a health facility she tested positive for malaria and had no signs of pneumonia. She was given intravenous artesunate for malaria but, because plague was suspected in the area, was admitted and started on gentamicin. About 8 hours later she coughed up blood-tinged sputum; other patients were moved out and droplet precautions began.
• Treatment. Gentamicin for 7 days and doxycycline for 4. She went home on March 14.

Confirming plague

The response

On March 5, UVRI and district staff traced contacts and handed out antibiotics.

During 10 days of follow-up, no contact developed plague-like symptoms, and active surveillance of clinics, communities and rodents found no plague activity in Uganda. The UVRI team could not work across the border in DRC, and what became of patient A's family and neighbors there, where plague was likely still circulating among rodents and fleas, is unknown.

What it shows

• Pneumonic plague is less contagious than its reputation. Only patient B fell ill, so the secondary attack rate among everyone with high-risk exposure was 2%. Estimates from outbreaks in Madagascar and Uganda are about 8%. Spread usually needs close, substantial contact with someone in late-stage disease; the highest-risk exposures are within 2 meters of a person coughing blood-tinged sputum, and traditional burial preparation may also carry risk. Cultural and behavioral factors can raise the risk.
• Modern tools control it. Droplet precautions, antibiotics and prophylaxis for contacts stop transmission. Contacts of patient A were 3–5 days past exposure when prophylaxis began on March 5; patient B fell ill about 72 hours after her exposure. Prophylaxis may have prevented illness in some, especially contacts of patient B, who were all still within the incubation period.
• Speed matters. Most plague follows a flea bite and causes bubonic plague: acute fever and a painful swollen lymph node, which untreated can spread to the lungs. Primary pneumonic plague usually incubates for under 1 to 4 days and is often fatal unless effective antibiotics start within 24–36 hours of onset.
• Diagnosis is hard, so use several tests. Without painful lymph nodes or bloody sputum the fever looks like many others. Here the rapid test, PCR and paired serology were all positive even though samples were taken after antibiotics began, which did prevent culture. The rapid test was used in joint CDC–UVRI research on its accuracy. Validated rapid tests in trained hands can guide a response quickly but should be backed by other tests.
• Local expertise pays off. CDC has worked with Uganda's Ministry of Health and UVRI since 2003 on plague surveillance in clinics and animals, laboratory capacity, community education and research. Working with community leaders, health workers and traditional healers helps catch cases early.
• Borders need agreements. The alert from DRC arrived, but no established cross-border collaboration let Uganda's resources and expertise help on the other side. All this happened while Ebola was spreading in DRC about 400 km to the south, which had heightened awareness of cross-border disease.

Sources

• Apangu T, Acayo S, Atiku LA, et al. "Intervention To Stop Transmission of Imported Pneumonic Plague — Uganda, 2019." MMWR 69(9). https://www.cdc.gov/mmwr/volumes/69/wr/mm6909a5.htm
• The report's summary says patient B was hospitalized 2 days after officials received the alert from DRC, while its narrative dates the alert March 1 and the hospitalization March 4; this page gives no interval. The report's figure is not reproduced, because it was prepared jointly with Ugandan institutions.