A 24-year-old man who tested positive for Ebola virus disease caused by Sudan ebolavirus (SUDV) was the first confirmed case in Uganda’s ongoing Ebola outbreak, but health authorities believe he was probably not the initial, or index, case. As of October 9, confirmed cases totaled 48, with 17 deaths, according to the Ministry of Health Uganda. But those numbers will likely continue to rise.

Uganda’s health authorities officially declared the outbreak on September 20. An approved vaccine for Ebola exists, but it is not effective against SUDV, the strain responsible for the outbreak. Several vaccines are in various stages of development against this strain, two of which could begin clinical trials in Uganda in the coming weeks, pending regulatory and ethics approvals from the Ugandan government and availability of doses for the trial. One is a single-dose vaccine that was developed by the Sabin Vaccine Institute. The other was developed by the University of Oxford’s Jenner Institute.

Although health authorities have attempted to reassure the public despite the lack of approved vaccines, the deaths of at least four health workers—including a doctor and a midwife—are raising concerns about the safety of frontline health workers who are responding to the outbreak.

Patrick Otim, health emergency officer of the Acute Events Management Unit at the World Health Organization’s Regional Office for Africa, says the response relies on the continual cooperation of the affected communities and the responders. So far community members have been cooperating, Otim says. “The teams that are [in] the field are receiving cooperation from the community in terms of investigation, listing of contacts and referral of suspected cases,” he says.

According to Uganda’s Ministry of Health, as of October 9, 1049 people who have been in contact with an infected person had been listed for follow-up, while 14 active cases had been admitted to the hospital for monitoring.

To prevent further spread, the response strategy prioritizes quickly identifying and isolating infected people, managing their care in treatment centers, engaging the community so that individuals can take preventive measures and ensuring that people comply with the public health interventions. “We believe that, by implementing these measures this time, [we should be] able to contain the outbreak without having much further transmission,” Otim says.

Scientific American spoke with Kyobe Henry Bbosa, Ebola incident commander at Uganda’s Ministry of Health, about the outbreak’s spread, as well as the country’s preparedness, response and public health strategies.

[An edited transcript of the interview follows.]

What do we know about how and when the outbreak started?

The epidemic seems to have started around early September, when people started dying in villages in the Madudu and Kiruma subcounties in central Uganda. The person with the first confirmed case presented to a regional referral hospital with symptoms of the disease after being treated in several places. Since we identified the SUDV at the Uganda Virus Research Institute, additional cases have been confirmed. The cases have come mainly from five subcounties in central Uganda’s Mubende district. We are also investigating cases that may have come from another neighboring district.

How does the epicenter of the current outbreak compare with that of previous ones?

The district lies on a major highway that leads into Kampala [the capital of Uganda] from the Democratic Republic of the Congo. It has busy trading places and a gold mine on one side, very close to the current epicenter of the outbreak. Uganda has had a number of SUDV outbreaks. The first was in 2000, when we had more than 200 deaths. The second one happened in 2012 in central Uganda, a bit farther away from this outbreak. And now we have the current one. Since the first one, we have gained significant expertise to be able to respond to this disease.

How has the COVID pandemic contributed to preparedness and response?

This current outbreak is happening just at the end of the peak of the COVID pandemic, which we think we managed successfully. We are quickly repurposing some of the infrastructure we used for COVID for Ebola. We now have significant capacity built across the country for protection and also to be able to galvanize committed support for a response. So we think that, using what we have done before, we should be able to appropriately respond to the current outbreak.

We have identified contacts, we are continuing to do contact tracing, and we are repurposing and extending the treatment center that had actually previously been used for COVID and enhancing public awareness.

What is the outlook for the outbreak? Is there a risk of cross-border transmission?

The 72 hours following the confirmation of the first case showed this is a rapidly evolving picture—very complex—the full extent and scope of which we don’t yet know. We think cases may rise in a few days without our full knowledge of the extent of contacts. But we’re working so much with the collaboration of other local and international partners to make sure that we care for people, that we ensure the safety of our health workers and, of course, that we bring this to an end as soon as possible so that we can protect our neighbor countries, and they don’t have to deal with cross-border transmission.

What do we know about what is driving the outbreak and its geographical reach?

Our investigations have not yet been able to identify the index case. We almost certainly know the virus was transmitted from a wild animal into the human population. Some hypotheses have been proposed relating to the country’s mango season. We are at the end of the mango season when people—mostly children—start to eat whatever they find [including fruit contaminated by an infected animal]. These are hypotheses that we are trying to work through to understand the origin of the outbreak and certainly find the index case. But we are currently primarily focused on contact tracing, caring for patients, protecting health care workers and providing information to people to prevent further spread.

This particular outbreak is most likely a spillover from wildlife. We have no evidence of this strain of Ebola virus in the recent past to suspect it came from a different outbreak. The last Ebola [Sudan ebolavirus] outbreak that happened in Sudan was more than 10 years ago, and we think it is much less likely to be a spillover from that. We think this is a fresh spillover from the wild into the human population, where it is currently circulating.

As for the geographical distribution, the main epicenter of the outbreak is Mubende district, which is near the center of Uganda. But within that, we have five subcounties [where cases have mainly occurred]. We are looking at a span of 70 kilometers from one end to the other. For the disease clusters within the subcounties, we are looking at a distance of up to 30 km. The breadth of response is the whole country. We are hoping to extend the response across the 11 districts surrounding the one at the epicenter.

Why did it take so long for the health authorities to flag the outbreak?

There is a little bit of time lag from what we think is a probable case to a real case. We can’t determine the index case until we confirm it. Ebola resembles most of the other tropical diseases such as malaria and typhoid. Initially, its presentation in the local setting appeared to be like other illnesses, and that contributed to a little bit of a delay. But as soon as the first confirmed case came to a major facility, we were able to diagnose Ebola.

This was, in a way, expected, largely because the individuals were mainly moving from one private health facility to the other seeking care. It was only when they reported to public health facilities that we were able to make a diagnosis.

With no approved vaccine for this strain, what is the plan to protect frontline health workers?

Those who are working in highly infectious settings have different sets of PPE [personal protective equipment] from those who are working in other areas of the hospital facilities. We have a sufficient amount of PPE. The WHO deployed an Ebola kit, which we are now using in the management of Ebola patients. But in addition, we still have leftover kits from COVID that we are still using.