Dalgard's Chronology of Events

Dalgard's Chronology of Events is Dan Dalgard’s personal computer diary of the unfolding disease among monkeys at the Reston Primate Quarantine Unit. Begun as deaths mounted in Room F, it records both close observations of the animals and the widening decisions made to protect workers and contain the outbreak. Its importance lies in the gap it preserves between what Dalgard could observe, what investigators could infer, and what remained unknown as events moved quickly around him.

Creation and form

Dalgard began keeping the diary soon after the deaths in the monkey house became a persistent mystery. He stored it on a personal computer and typed a few words each day, working quickly and with little deliberation. He gave it the title Chronology of Events. The title promises sequence, and the entries do establish a record of changing observations and decisions; yet the account is also an immediate working document, assembled while the meaning of the outbreak was still unsettled.

The diary’s physical form becomes part of the narrative at a moment when the investigation is expanding beyond the monkey house. On an evening after visiting the United States Army Medical Research Institute of Infectious Diseases, Dalgard returned to his office on Leesburg Pike, retrieved the floppy disk holding his diary, and put it in his briefcase. Later, at home, he inserted the disk into his computer and brought the record up to date. The sequence places the diary between two worlds: the institutional investigation and the domestic routine to which Dalgard returned. He had forgotten to tell his wife he would be late, stopped to buy carnations and mums, reheated dinner, and then resumed typing beside his clock-repair bench.

That juxtaposition makes the diary more than a retrospective chronicle. It is a record made by someone still managing ordinary obligations while trying to keep pace with a growing emergency. Dalgard’s difficulty keeping the day’s developments straight is itself part of the document’s context: the diary’s purpose is not to deliver a settled explanation, but to preserve the facts and questions that might otherwise become blurred as the situation changes.

Observing the monkeys

The entries preserve the gradual accumulation of evidence in Room F. Dalgard’s account describes animals that abruptly lost their appetites and became lethargic, then deteriorated quickly. Their temperatures were not elevated, and familiar outward signs such as nasal discharge, nosebleeds, or bloody stools were not evident in the observations recorded. Many were young, well-fleshed animals in apparently prime condition. The pattern was alarming precisely because it did not initially present as a clear, recognizable illness.

Dalgard’s examinations gave him more specific abnormalities to record without resolving their cause. The monkeys’ spleens were enlarged, unusually dry, and firm; kidneys were enlarged, and there were sporadic changes in different organs. When he returned to the building on Sunday, November 12, he found three more dead monkeys. He opened the body of Monkey O53, removed a piece of its spleen, and collected a throat wash with a Q-tip, preserving the sample in distilled water. These actions mark the diary’s transition from noting unexplained deaths to documenting material that could be examined for a cause.

The detail of the spleen is especially revealing of the limits of observation. Dalgard could record its size and hardness, but could not see what accounted for them. The book explains that the organ had become a solid clot of blood, a fact not available to him at the time. The difference between the diary’s recorded surface and the narrator’s later explanation gives the artifact a double function: it shows what the veterinarian encountered, while also exposing how much of the disease’s process remained invisible to the people examining it.

From notes to protective measures

As the deaths continued, the diary became a record of decisions, not only pathology. On November 16, after monkeys began dying in rooms beyond Room F, Dalgard received a tentative diagnosis from a pathologist: simian hemorrhagic fever, considered harmless to people but lethal to monkeys. He acted on the danger of further spread within the animal facility. That afternoon, he and another Hazleton veterinarian administered lethal anesthetic to the monkeys in Room F, then examined eight animals that had appeared healthy. Their bodies showed no apparent evidence of the suspected disease, deepening his concern about how little the visible condition of an animal could establish.

The record also tracks the shift in Dalgard’s judgment as concern reached the staff. When he learned that caretaker Jarvis Purdy had been hospitalized after a reported heart attack, he could not dismiss the possibility that Purdy was developing the same infection. Dalgard instructed the monkey-house manager to suspend unnecessary activity. Feeding, observation, and cleaning were to continue, but people entering the rooms were to wear protective suits, respirators, and gloves; dead animals were to be double-bagged and refrigerated. The diary captures these measures as specific instructions issued under uncertainty, before the cause of Purdy’s condition was known.

Dalgard’s notes also record his concern about communicating the danger without provoking panic. He did not want employees to leave the building in biohazard gear where news cameras might see them. He contacted Purdy’s doctor and asked that Colonel C. J. Peters be informed if the heart condition proved atypical, while avoiding the word Ebola in that conversation. The diary thus documents two kinds of containment: reducing contact with potentially infected animals and limiting the alarm that could follow from a public display of precautions.

The widening circle of uncertainty

By the evening Dalgard updated the diary on his computer, the questions had spread beyond the animals and the immediate caretakers. He had arranged respirators for the other monkey-house workers and briefed them on what was known about transmission of Ebola and Marburg to humans. He had also warned laboratory staff on Leesburg Pike, who handled monkey blood and tissue, to treat the samples as if they were infected with the AIDS virus. His notes raised the possibility that laboratories receiving animal shipments should report unusual deaths to the Centers for Disease Control and Prevention.

The record widens further through Dalgard’s unanswered questions about people who might have encountered the operation indirectly: workers on the air-handling system, the laundry service, and a telephone repairman whose visit he could not date precisely. These possibilities are not confirmed exposures. Their presence in the diary matters because it shows Dalgard trying to map the boundaries of risk while acknowledging how incomplete his information was. He asks whether anyone has been overlooked, rather than presenting the contact network as already understood.

That uncertainty continued when Nancy Jaax later told him that the tissue findings were consistent with either simian hemorrhagic fever or Ebola, possibly both. Her results were ambiguous. The diary therefore stands at an important point in the investigation: the initial diagnosis had not settled the identity of the agent, and the evidence available from tissue did not yet resolve the question. The entries make the changing state of knowledge visible without converting a provisional judgment into certainty.

Documentary and narrative significance

The book uses Dalgard’s Chronology of Events as a counterweight to its broader, more dramatic account of viral danger. The diary’s details are practical: appetite, lethargy, organ changes, protective equipment, sample handling, and the names of people whose health or work might be implicated. Its title suggests an orderly sequence, but its subject is an emergency in which observation and interpretation repeatedly fail to line up. Animals could look healthy and still be part of a deadly outbreak; an illness described as a heart attack could raise an unresolved question about infection; a laboratory finding could remain compatible with more than one diagnosis.

The diary also provides a human measure of the administrative burden. Dalgard moves from examining carcasses and speaking with Army investigators to considering hospital notification, staff protection, public attention, and possible contacts he cannot even date. At home, he tries to reconstruct the day from a floppy disk because events have become difficult to hold in memory. The form is modest, but the task it records keeps expanding: to preserve what happened, distinguish what is known from what is suspected, and make decisions before certainty arrives.

As a result, the diary functions both as evidence within the outbreak narrative and as a portrait of investigation under pressure. It does not solve the mystery by itself, nor does it claim to. Its significance is the disciplined record of changing knowledge: an evolving account in which observed facts, tentative diagnoses, operational choices, and unanswered questions remain side by side.