Uganda: Three questions for an MSF epidemiologist about the new Ebolavirus variant

“We never know everything about the epidemiological puzzle.”

Ebola outbreak in Uganda, Mubende Ebola Treatment Center

Uganda 2022 © Sam Taylor/MSF

It has been over two weeks since the last confirmed Ebola case—a stillborn baby of a mother who survived the disease—was reported in Uganda. Doctors Without Borders/Médecins Sans Frontières (MSF) has been responding to the rare outbreak of the Sudan Ebolavirus variant since it was declared on September 20 by building Ebola treatment centers and treatment units, providing support to the Ugandan Ministry of Health for case management in these facilities, and conducting community outreach activities like health promotion and infection protection and control measures in health facilities where known patients went prior to diagnosis.

Denis Ardiet works for Epicentre, MSF's epidemiology division. He currently coordinates a team of seven epidemiologists involved in the ongoing Ebola response in Uganda. His job involves rigorous analysis of the epidemiological situation and the possible scenarios of this outbreak to help inform how MSF and the Ugandan Ministry of Health can respond accordingly.

What is the current trend of the outbreak in Uganda?  

In terms of trends, we saw two important peaks in the outbreak. The first one was in September in the Mubende district, which was the first epicenter of this outbreak, and then another in the neighboring district of Kassanda. While cases in these two districts alone represent 80 percent of all cases detected so far in this outbreak, a total of nine districts in the country were affected. Historically, this is the largest geographic spread of Ebola that Uganda has ever faced.    

After a steep rise of cases in October (86 cases over 4 weeks), the outbreak slowed in terms of numbers of new confirmed cases in recent weeks (14 cases in 4 weeks in November). However, we are very concerned that we had several Ebola cases that were not linked to any known chains of transmission—this means they had acquired the infection from an unknown source, which means those cases couldn’t be tracked through contact tracing and follow-up. This led to two new districts being affected, Masaka and Jinja.    

What epidemiologists do to help curb Ebola outbreaks

During an outbreak, epidemiologists document each case and their contacts for follow-up over time and place to ensure the overall understanding of the outbreak spread is as comprehensive as possible. 

The work consists of collecting data to produce maps and epidemiological curves, which inform MSF’s response on a daily basis.

Thorough investigations of each Ebolavirus patient’s history must be done to link them back to previous cases and to anticipate where the disease could spread, based on the person’s previous movements and contacts.

Epidemiologists also work on understanding the context and gathering qualitative data on community perceptions of preventative measures and outbreak response policies.

Understanding and interpreting this information on a global level is how MSF helps to support the Ugandan Ministry of Health. 

It’s extremely important to follow up with case contacts. When we identify all the people who were in contact with a confirmed case in time, we can monitor their health and help them to seek care swiftly at the right health facility in case Ebola-related symptoms develop. Yet according to the Ministry of Health data, only around 64 percent of case contacts initially received follow-up, pointing to gaps in this crucial part of the response. While the overall epidemiological trend is now positive, we remain concerned and vigilant about what could still happen.   

What are possible future scenarios?

Anything is still possible. Scenario one is that we see a continued downward trend and no more new cases as we approach the end of the epidemic. Scenario two is that occasional new cases emerge here and there, perhaps in different districts. And scenario three is that there is an increase in new cases moving toward another peak in transmission.

All of these different scenarios will require corresponding operational responses from MSF teams and Ministry of Health teams that we work with very closely. We rely very much on their data, especially since we do not run our own laboratory testing or our own case investigations.

How MSF can best support the Ugandan health authorities depends on the needs of the situation. We must evaluate what makes the most sense and we might switch to a smaller scale rapid response team-approach. This could be a more community-based approach closer to where patients live rather than having sizeable treatment centers set up within the districts.

Ebola outbreak in Uganda, Mubende Ebola Treatment Center

A patient’s room in the MSF-supported Mubende Ebola Treatment Center. Uganda 2022 © Sam Taylor/MSF

Ebola outbreak in Uganda, Mubende Ebola Treatment Center

To avoid any risk of contamination, a nurse is dressed with a Personal Protective Equipment (PPE) before he enters the area of the Mubende Ebola Treatment Center where patients infected with Ebola are being cared for. Uganda 2022 © Sam Taylor/MSF

It is also essential to ensure that non-Ebola care continues in the affected areas and that curative and preventive management of malaria cases is in place, given that initial symptoms for Ebola and malaria are similar. We support the Ministry of Health in reinforcing case detection and isolation capacity in existing health facilities so they can react promptly to any new alert or case and quickly reduce the chances of wider spread. On the community side, the Ministry of Health sustains health surveillance to make sure there is no ongoing transmission. All these efforts must be vigilantly maintained until the epidemic is officially declared over—after 42 days without new cases, or twice the Ebolavirus incubation period of 21 days.

We never know everything about the epidemiological puzzle, and we can only make sure we gather as much relevant information as possible. We are aware of the epidemiological situation, and we see that the epidemic curve has descended, which is good. But behind this curve, there may be events and information we don’t know—and that is the difficult part to uncover. Regardless, we have to be prepared and reactive to respond to any alert or new case.

Is a rapid decrease of cases unusual in Ebola outbreaks?

It has been observed during other outbreaks, even though it remains surprising considering all the unknown elements at play in the Uganda outbreak. Such a decrease may reflect that transmission has stopped through a combination of several factors, including the outbreak response and community actions. This outbreak reminds me a bit of those in Conakry in Guinea in 2015 or Beni in the Democratic Republic of Congo in 2020. The health authorities and their partners, including MSF, also had difficulties in following up all case contacts back then and despite decreasing trends, the final few cases popped up sporadically for some months.

One month of MSF Ebola response in Uganda, 2022

An MSF health promoter speaks with a shop keeper in Madudu, close to the epicenter of the Ebola outbreak in Uganda. 2022 © MSF/Sam Taylor

It is important to mention that the initial low rate of case contact follow-up in Uganda has in fact improved over the last weeks in several districts. While that is a good sign, it still seems that the response often focusses on demanding community adherence to follow-up either through obligatory quarantine or home isolation and daily calls which can scare people when empathetic and comprehensive health messages that explain the rationale of these measures is not shared. Health promotion and community outreach activities play an essential role to bridge this trust gap and ensure that people have sufficient information about the Ebolavirus to protect themselves and their communities, and to better understand the measures.

Usually—as can be the case in any outbreak and as we also saw with COVID-19—there is a lot of fear around the prospect of being removed from your family and friends, isolated and sent to an Ebola treatment unit. Health promotion and community engagement helps to counteract rumours and fears while supporting the prevention of community transmission.