At the end of August 1976, Mabalo Lokela, a forty-four-year-old teacher, returned from his travels, with a high fever. He had been travelling in the north of Congo near the border with the Central African Republic. The medics who examined him in the mission hospital in his home town of Yambuku suspected that he had contracted malaria, so he was given a shot of chloroquinine. His temperature came down, so he was released from the hospital and left to home care, but after only a few days the fever came back.
In the beginning of September his family brought him back to the hospital, but by then he was already in very poor condition. He vomited uncontrollably, had acute diarrhea, headaches and trouble breathing. In the days that followed his nose, eyes and gums began bleeding. Unfortunately, there were no doctors in the mission hospital, only nurses, so although they did everything in their power to help him they were unable to diagnose or treat the disease effectively. On September 8, approximately two weeks after presenting the first symptoms of the illness, Mabalo died.
“We’re all going to bleed to death!”
In keeping with tradition, Mabalo’s wife Mbunzu, who took care of him all along, washed her husband’s body with her mother, her husband’s mother, her sister and other close female relatives to prepare him for his funeral. Soon after the funeral, they along with other relatives and friends who were present at the ceremony all developed the same symptoms as those the deceased teacher had died from only a couple of days earlier. Some nurses from the hospital where Mabalo was being treated also fell ill. People started to panic; it seemed that they were all going to bleed to death.
On September 15, Dr. Ngoy Mushola, a doctor from the nearby town of Bumba, came to Yambuku at the request of the director of the mission hospital. He realized quickly that they were dealing with a case of a highly contagious disease, one that was already spreading rapidly through the town and the neighboring villages. He wrote down a detailed description of the symptoms and tried imposing at least a minimal quarantine upon afflicted people. This was necessary because the locals were used to burying their dead right next to their houses or even inside their dwellings, and this only accelerated the rate of infection. On 17 September Dr. Mushola sent his first official report of the outbreak of this contagious disease to those responsible in Kinshasa and requested immediate assistance.
On 23 September two experts on microbiology and epidemiology, otherwise professors at the National University of Zaire, came to Yambuku to assess the situation. After they arrived, they diagnosed the illness as an outbreak of atypical yellow fever and soon left the area of epidemic. They brought a very ill nurse and two other members of the staff from the mission back with them to Kinshasa. The samples of the diseased nurse’s blood were then sent to the Pasteur Institute in Paris through the French Embassy in the hope of a precise diagnosis. Analysis of these samples at the Institute revealed that the disease was caused by a completely new virus. The disease was named Ebola after a stream in the vicinity of Yambuku from which it was thought to originate.
Shortly afterwards, at the beginning of October, the local authorities brought in the army isolate Yambuku and the surrounding area with road blocks. Movement was also restricted in the larger nearby town of Bumbu, two field hospitals were set up as quarantines, and travel to other parts of the country was prohibited. Despite these efforts, the disease continued spreading to many nearby villages, infecting 318 people of which 280 (almost 90%) died.
At the same time, a slightly different strain of the virus spread from this area in the heart of Africa to the south of Sudan. The Sudanese manifestation of Ebola was slightly less deadly, with a mortality rate of just over 50%. But still, out of 284 people who caught the disease 151 died.
The monkey connection
Virologists studying this strange and frightening new killer illness in northern Congo and southern Sudan presently discovered that the virus was similar to one that had appeared in Europe barely a decade earlier. In 1967 in Marburg, Germany, the local clinic for infectious diseases had admitted a number of severely ill patients running very high fevers, suffering from great pain and eventually bleeding from several parts of the body. It turned out that all of them worked at the same pharmaceutical company and had been infected by a virus they had contracted from monkeys imported from Uganda. Half of the monkeys, which were needed to prepare the cell cultures for use in producing vaccines, had already died on the way from Africa.
Apart from Marburg, some cases of infection with the same virus were also discovered in Frankfurt and Beograd. Twenty-five people were infected by direct contact with the monkeys and seven did not survive. Besides these primary infections, six more individuals fell ill, but there were no more deaths.
When it comes to outbreaks of this deadly viral disease, the one fortunate thing is that the Ebola virus kills too rapidly to spread effectively among people. The infected individual quickly becomes too weak and ill to walk around spreading the infection, so Ebola viruses are thankfully limited in scope. From 1976 less than 2000 people contracted Ebola, but the mortality rate of each outbreak was as high as 50-90%. One of the highest death rates was recorded during the 1976 outbreak in Congo.
Could bats be the carriers?
Although we are much more familiar today with the ways such fatal diseases function and spread than we were decades ago, in African countries outbreaks of Ebola and similar viruses still occur. In 2007, around a hundred people were afflicted by Ebola, a quarter of whom died. In the middle of July 2008, a Dutch woman who had returned from her travels in this African country also died from an Ebola-like virus. She was thought to have been infected by a bat during a visit to a cave.
On the HealthMap website (www.healthmap.org) a map of the world enables us to keep track visually of the latest reported outbreaks of disease. The website automatically tracks professional health information sources and warnings as well as newspapers and other news sources, classifies outbreaks according to the level of danger and locates them on the map. At the beginning of this summer, a red flag marked the Dutch city of Leiden where local doctors wearing protective gear in a specially secured part of the main hospital were treating the infected tourist mentioned above.
Humans are not the only species in need of a vaccine against Ebola, since it not only attacks people, but can also affect monkeys and forest antelopes. The disease poses a significant threat, for example, to the gorilla population. There is thus an element of environmental conservation as well as public health in the fight against Ebola.
One of the more important questions concerning Ebola and similar diseases is what species is their original natural host and how the viruses are then transmitted to other species. For some time now it has been suspected that the natural carriers of this disease are bats, but the hypothesis has yet to be confirmed. However, it has been established that bats are not affected by the disease even if they carry the virus. One of the first cases of infection in Sudan in 1976 was an employee of a cotton factory which contained a large number of bat-nests. It has also been suggested that forest-dwelling animals might contract the virus by collecting and eating fruits that have already been chewed on and cast off by bats. The teacher Mabalo Lokela, who was officially the first to have died from Ebola was thought to have eaten antelope meat during his travels in the northern part of Congo.
For exceptionally dangerous diseases such as Ebola or anthrax, the American Food and Drug Administration (FDA) even changed its rule of only approving a vaccine once it has been successfully tested on people. For these especially lethal diseases vaccine production may go ahead if scientists prove that an experimental drug successfully immunizes two species of animals. Naturally, it would be difficult to find someone who would be brave enough to take an injection of such a prototype vaccine and then be voluntarily infected just to prove that the vaccine really works.