Second Reston outbreak period (January–March 1990)

The Second Reston outbreak period (January–March 1990) was a second wave of Ebola Reston virus infection in a Virginia monkey house, following the first outbreak and the Army’s cleanup of the facility. It became an unintended observation of what the virus could do in a confined monkey population: it spread through multiple rooms, appeared to change its clinical character, and infected four human caretakers without making them ill. The decision to isolate the monkeys rather than immediately clear the building made the outbreak both a containment problem and a natural-course experiment whose implications remained unsettling.

Recurrence in the monkey house

In January 1990, after the United States Army had certified that the monkey house was cleared, the facility returned to Hazleton Research Products. The company began bringing in more animals from the Philippines, from the same monkey house near Manila, and restocked the building with crab-eating macaques trapped in the rain forests of Mindanao. Less than a month later, in mid-January, monkeys in Room C began dying with nosebleeds. Dan Dalgard notified Peter Jahrling that the building appeared to be affected again; testing showed that Ebola had returned.

The renewed outbreak followed a short interval between clearing the building and reintroducing animals. The book presents the new monkeys’ origin and the timing of their arrival as the setting for the recurrence, identifying the virus as having come from the Philippines. It does not establish the precise route by which the animals became infected before or during their arrival. The return of illness nevertheless made the facility’s apparent clearance feel provisional: the virus had again appeared in a population housed within the same building.

A deliberate change in response

Because the first outbreak had produced no human casualties, Hazleton, the United States Army, and the Centers for Disease Control and Prevention jointly chose a different course. They isolated the monkeys, left them alone, and allowed the infection to burn through the population rather than immediately sending in military personnel in protective suits. Dalgard hoped that at least some of the animals might survive, and Hazleton wanted to avoid another Army intervention. The decision also meant that the virus could be observed in a confined population over time, rather than being interrupted by an immediate clearing operation.

That choice did not make the situation safe or predictable. The facility became an experiment in the limited sense described by the account: researchers could watch the infection move through a monkey population living in a shared indoor environment. The decision reflected competing practical concerns—animal survival, the company’s wish to retain control of its facility, and the need to understand an infection that had returned. The outbreak’s course supplied information, but at the cost of allowing the disease to continue among the animals.

Spread and changing symptoms

Ebola Reston virus moved rapidly from room to room. In affected monkeys, the illness sometimes resembled a severe respiratory disease, with substantial nasal mucus and pneumonia. The lungs of infected animals were badly affected. When a monkey with a nosebleed appeared in a room, the account reports that about 80 percent of the animals there generally died soon afterward. This pattern showed how quickly infection could become widespread within the facility, even as the visible symptoms seemed different from those observed during the earlier outbreak.

By January 24, infection had reached Room B, where monkeys began to become critically ill. In the weeks that followed, the virus entered Rooms I, F, E, and D; virtually all of the animals in those rooms died. Researchers suspected that they were seeing a mutant form of Ebola, distinct in some respects from the virus observed in December. The account treats rapid alteration as a serious possibility, not as a fully explained mechanism: the new outbreak suggested that the virus could appear to change character in a short time and adapt in a new host population.

Human exposure and the outbreak’s end

In mid-February, caretaker John Coleus cut his thumb with a scalpel while conducting a necropsy on an infected monkey. The blade had been used on the liver, an organ in which Ebola commonly concentrated, and the exposure was considered major. A sample of the liver was taken to the United States Army Medical Research Institute of Infectious Diseases, where Tom Geisbert found it heavily laden with virus. Despite the concern surrounding Coleus’s exposure, he remained well and ultimately suffered no ill effects. He underwent surgery for an unrelated medical condition during the incubation period, with no record of excessive bleeding.

Coleus’s case was only one part of the human outcome. Four men who had worked as caretakers in the monkey house—Jarvis Purdy, Milton Frantig, John Coleus, and a fourth worker—eventually tested positive for Ebola Reston virus. None became ill, and the virus later disappeared from their blood. Coleus had sustained a cut, but three of the four men had not. Because their infections could not all be explained by cuts, researchers at the Institute concluded that transmission through the air among monkeys was a likely explanation for how the virus reached the workers. The account presents this as a consequential inference from the pattern of infection, rather than a complete explanation of every transmission route.

By the time the second outbreak ran its course, the monkey house’s population had died out. The Army did not need to clear the building again: in the book’s account, the virus had effectively done so. There were no human casualties, but the infections in caretakers showed that absence of symptoms did not mean absence of infection. In March 1990, the Centers for Disease Control and Prevention tightened testing and quarantine rules for imported monkeys and temporarily revoked the licenses of Hazleton Research Products and two other companies, Charles River Primates Corporation and Worldwide Primates. The suspensions were later lifted, but monkey imports into the United States stopped for several months, and Hazleton suffered losses running into the millions of dollars. The company later vacated the building, which remained empty.

Significance and unresolved questions

The episode sharpened the distinction between Ebola’s effects in monkeys and its effects in people. Four workers carried the virus without recognized illness, even though the disease had devastated the monkey population. The book leaves unexplained why the workers remained symptomless and emphasizes that infection in a person could not be dismissed simply because no symptoms appeared. The event thus complicates a straightforward account of Ebola as a single, uniform threat: within the same outbreak, the agent could be lethal to monkeys and apparently mild in infected people.

The recurrence also sits within the book’s wider account of human contact with wildlife and changing ecosystems. Its discussion of tropical forests describes habitat loss, wildlife capture, and the trade in primates as circumstances that bring people and animals into closer contact, while stressing that the origins and routes of particular viruses may remain unknown. That context does not establish the exact source of the virus in this outbreak. It instead makes the return of Ebola in imported monkeys part of a larger pattern of risk in which animal movement, confined populations, and human systems of trade and research can create opportunities for viruses to circulate. The second outbreak ended without human illness, but its record of extensive monkey mortality, caretaker infections, and probable airborne spread left the event far from reassuring.