Mortality after an Ebola infection is very high, which is why the disease is also known as the “killer virus”. There is now a major Ebola outbreak in Congo.
May 20, 2026, 06:41May 20, 2026, 06:41
Ebola once made it to Switzerland: two infected people were treated here. The Basel epidemiologist Marcel Tanner, former director of the Swiss Tropical and Public Health Institute, was involved in one of these cases.
Medical staff and soldiers in North Kivu province in the Democratic Republic of Congo.Image: keystone
The World Health Organization (WHO) has now declared a public health emergency due to the Ebola outbreak in the Democratic Republic of Congo and Uganda. This outbreak was caused by the Bundibugyo Ebola strain. The increasing trend of suspected cases and deaths in Ituri indicates that the outbreak may be much larger than previously discovered and reported, according to the WHO. We answer the most important questions with the Basel epidemiologist and Africa expert Marcel Tanner.
Marcel Tanner, epidemiologist and former director of the Swiss Tropical Institute.Image: Annette Boutellier
How many cases are there currently?
The health authorities report that there have been eight confirmed and 246 suspected cases of the dangerous fever disease in Ituri province in northeastern Congo. In addition, a case has already been detected in the distant capital Kinshasa, and two infected people from the Congo have traveled to Uganda. The WHO reported 80 Ebola deaths in Ituri so far. The African health authority Africa CDC recently reported slightly higher numbers for the Democratic Republic of Congo, namely 336 suspected cases and 88 deaths.
What kind of Ebola variant is this?
The Bundibugyo variant is rare. The most common is the Zaire variant, which is more dangerous than Bundibugyo.
What symptoms does the Ebola virus cause?
After infection, it takes around 8 to 10 days for the first symptoms to appear. At the beginning there is a sudden increase in fever, with headache and sore throat as well as muscle and joint pain. After about four days, nausea, diarrhea and vomiting occur. Bleeding occurs in some patients. Multi-organ failure of the kidneys, liver and circulatory system leads to death in half of those affected by the Bundibugyo virus. This usually occurs 6 to 16 days after the onset of symptoms.
Is the disease less severe with the Bundibugyo variant?
No. With these so-called hemorrhagic viruses, which include Ebola, mortality varies, but often the severity of the disease does not. “If you can’t do anything about the disease, the risk of mortality from the Zaire virus is between 50 and 80 percent. At Bundibugyo 30 to 50 percent,” says Marcel Tanner. Up to half of those affected can die from the Bundibugyo variant, which shows how dangerous this variant is.
Where do the Ebola viruses come from?
Fruit bats are a reservoir for Ebola viruses. In the so-called zoonosis, however, these do not spread directly from animals to humans, but rather first to other animals. However, all animals, both antelopes and monkeys, can get Ebola, including humans. The Ebola virus often jumps to him via hunting. The hunter usually catches the weaker animals and not the healthy ones. “So the risk that the animal is infected with Ebola is greater,” says Tanner. If the animal is ultimately shared in the village and eaten by many, many will become infected. Many people in the village fall ill and die from it. Nevertheless, the virus usually stays in the village and does not spread across the country if people do not travel.
How do you get infected with Ebola?
In contrast to the corona virus, which is transmitted from person to person via droplets, Ebola requires closer contact via body fluids. The Ebola virus is in the blood, urine and stool, sweat and sperm. Epidemiologist Tanner has an example: An infected man flew from Liberia to Nigeria, to Lagos. He vomited on the plane, which led to 13 subsequent cases in Nigeria. There was quickly panic that the virus could spread in the poor areas of Lagos. The Unicef contact tracers clarified 9,000 cases, which is why there was no epidemic.
What to do in an Ebola outbreak?
Rapid local treatment, isolation, protective clothing and infectious agents as well as good clinical, symptomatic care, especially fluid intake. This means that outbreaks have always been kept under regional control. This becomes more difficult when people in Africa leave their villages and become mobile. This happened primarily in West Africa between 2014 and 2016. The worst Ebola epidemic since the virus was discovered resulted in around 11,000 deaths from the Zaire variant. The system of local, peripheral care collapsed there, medical posts were closed because, for example, the employees had no disinfectants and were no longer paid. The Ebola sufferers then traveled to the big cities and spread the virus throughout the country. “The transmission was easy in the bush taxis, that happened in 2014 and 2015,” says Tanner. In a short time, the Ebola virus was in the slums of Monrovia.
Why have there been no Ebola pandemics so far?
A country’s health authority can get the virus under control using the classic methods of isolation, disinfection, symptomatic treatment and care during burials. For example, explaining to people that they should no longer hug the dead at funerals, as is their culture. However, the risk of an epidemic is constantly increasing in Africa because the areas are becoming more densely populated and isolating Ebola patients is becoming more difficult than in a village in the steppe. As with Corona, with Ebola it is important to quickly discover where the sources of infection are in order to take immediate action. Consistent contact tracing is also important, with which contacts of Ebola infected people are quarantined. Then a spread, a pandemic across the entire continent, is not to be expected.
Why is Ebola hardly in Europe and Switzerland?
There is a effective strategy in Switzerland against hemorrhagic viruses. University hospitals have the option of isolating Ebola patients. This happened in two cases. In 1994, a veterinarian from Ivory Coast and in 2014 the doctor from Cuba who became infected in Sierra Leone were nursed back to health in isolation in Basel and Geneva.
Is there a vaccine against Ebola?
There is no vaccine against the Bundibugyo variant. On the other hand, there are two vaccines against the Zaire variant. The one from Johnson&Johnson against the most dangerous strain was approved in 2020 and is used in particular for exposed personnel. Vaccine development for Bundibugyo virus and other species is still in clinical testing phases.
What does the therapy look like?
There is no specific therapy for the Bundibugyo virus. Treatment is symptomatic. The virus enters the vascular cells and when it multiplies there, it destroys the cells and, among other things, triggers the bleeding typical of hemorrhagic viruses. Most have a very severe fever, which is treated with fever and anti-inflammatory drugs. There is also off-label use of antiviral substances. For example, the drug Remdesivir. In the case of Ebola, it was able to reduce the severity of the disease. Favipiravir, originally developed to treat the flu, also appears to work. In the case of Ebola, these drugs were able to reduce the severity of the disease, but they must be administered early. Two monoclonal antibody preparations that are approved for the treatment of the disease caused by the Zaire virus are also used.
Can the infected people in Congo be helped?
It is currently difficult to care for Ebola patients in the complex eastern Congo because various rebel groups are active there. It is then difficult for doctors from Médicins sans Frontière and the WHO to get to the affected villages. The socio-political instability favors an Ebola outbreak like the one that is currently taking place.
Are there other zoonoses than those with Ebola viruses?
Of 1,400 infectious diseases, 800 are zoonoses, i.e. transmission from animals to humans. Only a few of these have spread to humans: including Ebola, Mers, bird flu, Sars-1, Sars-2, Nipah and rabies. There are hundreds more that humans could pick up through contact with the ecosystem. After the zoonosis, what is crucial is how the virus then transmits from person to person. This was bad with Sars-1, but very easy with Sars-CoV-2. (aargauerzeitung.ch)