The narrative now flashes back to 1976 and the outbreak of two strains of the Ebola virus, beginning with Yu G. A quiet storekeeper in the town of Nzara, Sudan, Yu G. dies at home from Ebola and is buried in a traditional Zande funeral. It is unclear where or how Yu G. becomes infected, but a few days after his death, two of his co-workers develop similar symptoms. One of these men, known as P.G., has a wide circle of friends and exposes many people in the town. Before long, the Sudan strain of the virus has traveled to a hospital in the town of Maridi, where it quickly spreads through the medical staff and patients. The outbreak ends only when the surviving medical staff abandons the hospital and inadvertently break the chain of infection.
Two months later, there is another outbreak of the Ebola virus in a district of Zaire called Bumba. Nearly twice as deadly as the Sudan strain, Ebola Zaire initially surfaces at the Yambuku Mission Hospital, where Belgian nuns are treating hundreds of villagers with the same five hypodermic syringes. The virus breaks in 55 villages simultaneously, first appearing in individuals who received injections from the nuns, then in their family members, and then in the nursing staff and nuns.
Sister M.E., one of the infected nuns, is taken to the city of Kinshasa so she can receive better medical care. She checks into Ngaliema Hospital where she soon dies. While the medical staff is unable to identify the exact cause of the nun’s death, the doctors suspect a replicating virus similar to Marburg. Soon afterward, Sister E.R., a nun who accompanied Sister M.E. to the hospital, also develops symptoms and dies while under the care of Nurse Mayinga.
Nurse Mayinga is unable to accept that she has been infected by the virus, even though she is already exhibiting the early stages of illness. She leaves her job at the hospital and wanders through the city, first attempting to confirm travel papers to Europe and then receiving treatment for her worsening symptoms at another hospital. After two days, Nurse Mayinga returns to Ngaliema Hospital where she is admitted as a patient. The government realizes the potential for a devastating outbreak and immediately places the hospital under quarantine and establishes roadblocks to seal off Bumba.
Nurse Mayinga falls under the care of Dr. Margaretha Isaacson, who initially treats her while wearing a gas mask. Unable to function well in the oppressive heat, Dr. Isaacson eventually abandons the mask and treats her patient face-to-face. Despite Dr. Isaacson’s best efforts, Nurse Mayinga dies from a heart attack caused by the virus. Dr. Isaacson realizes that she is likely already infected and takes it upon herself to clean Nurse Mayinga’s blood-spattered room, as well as the private rooms used for Sister M.E. and Sister E.R., to save anyone else from contracting the disease.
Meanwhile, doctors at Ngaliema Hospital perform an autopsy on Sister M.E. and send samples of her blood to laboratories in Belgium and England in order to identify the virus. At the Special Pathogens Branch of the Centers for Disease Control (C.D.C.), Karl Johnson manages to acquire a small sample of the nun’s blood from one of his colleagues at the English laboratory. Patricia Webb and Frederick Murphy both examine the blood, and Murphy immediately notices the virus’s similarity to Marburg. When the virus does not respond to any tests for Marburg, the scientists realize that they have identified and isolated a new organism. Johnson names the virus “Ebola.”
Two days after isolating the Ebola strain, Johnson travels to Zaire with Joel Bremen, another C.D.C. doctor, in an effort to stop the outbreak of the virus. While Johnson becomes the head of an international World Health Organization (WHO) team based in Kinshasa, Joel Bremen joins a field exploration team to discover the extent of the outbreak in Bumba. After a short plane ride, Bremen and his team slowly proceed into the forest to Bumba and the Yambuku Mission Hospital. When Bremen and the rest of the team arrive in Bumba, they discover that the epidemic has peaked and most of the infected people are dying or already dead.
Like the strains of Ebola Sudan and Ebola Zaire, which disappear after the outbreaks in Nzara and Bumba, the Marburg virus vanishes after the initial outbreak in Charles Monet. Yet in 1987, the virus reappears in Peter Cardinal, a ten-year-old Danish boy who dies at Nairobi Hospital under the care of Dr. David Silverstein. Eugene Johnson, a biohazard expert at USAMRIID, receives a sample of Peter Cardinal’s blood shortly after the boy’s death. After isolating the strain, Johnson is able to identify the virus as Marburg. Johnson contacts Dr. Peter Tukei, a colleague in Kenya, in order to learn where Peter Cardinal might have been exposed to the virus. Dr. Tukei discovers that, like Charles Monet, Peter Cardinal had spent time inside Kitum Cave.
Gene Johnson and Dr. Tukei organize a scientific expedition to Kitum Cave with the goal of uncovering the source of the Marburg virus. Aware that Marburg can travel through the air, Gene Johnson requires the members of the expedition to wear breathing apparatus inside the cave. The expedition also includes a number of "sentinel animals", including monkeys and guinea pigs, which are placed at the mouth of the cave as a first alert system of disease. The team members test cave crystals, thousands of insects, hundreds of small animals, and even the local villagers and cattle in the hope of finding the Marburg virus. Yet, Gene Johnson and Dr. Tukei are unable to find any trace of the virus. Even the sentinel animals remain healthy throughout the entire operation. While he is unable to prove it, Gene Johnson is still certain the Marburg virus lives in the shadow of Mount Elgon.
In this section of the book, Preston introduces the reader to Ebola Sudan and Ebola Zaire, both of which are far more lethal than the Marburg virus. As he did with Charles Monet and the Marburg virus, Preston highlights individual characters from each outbreak in order to dramatize the scene beyond a simple non-fiction narrative. This also helps the reader to put a face to each strain of the virus, as well as providing necessary context for the scenes featuring both strains during the Reston operation.
In both Sudan and Zaire, human negligence plays a substantial role in promoting the spread of the virus during the outbreaks. When Ebola Sudan appears in the Maridi Hospital, it spreads as a direct result of the medical staff's use of dirty needles. In an almost identical scenario, Ebola Zaire breaks in the district of Bumba when dirty needles are used at the Yambuku clinic. In both cases, a site that should have been an example of prevention against these viruses was ultimately the cause of greater infection.
These medical facilities are in direct contrast to the Nairobi Hospital, where both Charles Monet and Peter Cardinal receive treatment without anyone else dying. Yet, this contrast speaks to the income inequality and varying level of health care present in the smaller districts and rural villages of the region. Ebola Zaire is able to break in 55 villages simultaneously only because all 55 villages are served by a single medical clinic. While the Belgian nuns, Peter Cardinal, and Charles Monet are able to afford airplane flights to locations that offer “better medical treatment” (104), the residents of Bumba and Nzara have no option outside the clinics in their area. This inequality of health care is particularly clear in a comparison of death rates: while more than 430 individuals died of Ebola Zaire and Ebola Sudan in rural villages, only 3 people died of the virus at Ngaliema Hospital.
In the scene with Nurse Mayinga and Dr. Isaacson, Preston highlights the varying ways in which individuals deal with certain death. While Mayinga is unable to accept the truth of her situation, Isaacson immediately recognizes the likelihood of her exposure and elects to spend her time being useful. Part of this difference can be attributed to age and milestones already achieved in life. While Nurse Mayinga is barely in her twenties and dreams of studying in Europe, Dr. Isaacson is past the prime of her life and already has adult children. Yet again, Preston demonstrates the indiscriminate nature of the Ebola virus: while the young, hopeful Mayinga treats a dying patient only to die herself, the middle-aged Dr. Isaacson avoids even becoming infected.
Throughout this section, Preston reminds the reader of the lack of knowledge about filoviruses. Although Yu G. is clearly the index case (first recorded patient of an outbreak) of Ebola Sudan, the original cause of his infection cannot be identified. The cause of the outbreak in Zaire is even more vague, as Preston can only hypothesize that one of the hundreds of villagers injected at the clinic was somehow exposed. Even Gene Johnson is unable to discover the source of the Marburg virus, despite an extensive team of scientists and proof that both Charles Monet and Peter Cardinal visited Kitum Cave. As a result, the reader is forced to consider the power of the filoviruses as a largely unknown entity.