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Ebola Virus Infection in Imported Primates -- Virginia, 1989

In late November 1989, Ebola virus was isolated from cynomolgus monkeys (Macaca fascicularis) imported into the United States from the Philippines via Amsterdam and New York. During quarantine in a primate facility in Virginia, numerous macaques died, some with findings consistent with simian hemorrhagic fever (SHF). The U.S. Army Medical Research Institute of Infectious Diseases tested 10 animals and, from three, isolated SHF from tissues and serum; however, five other animals of the 10 tested were positive for Ebola virus. Monkeys from a later shipment quarantined in a second room also had unusually high mortality and were tested by a rapid antigen detection enzyme-linked immunosorbent assay. Ebola viral antigen was detected in serum and/or tissues from seven of these monkeys. Primary liver material from animals in both rooms exhibited particles with typical filovirus morphology by electron microscopy and Ebola virus antigen by immunohistochemistry.

All persons who might have come in contact with the monkeys or with tissue or blood specimens from them have been identified and will be under surveillance by the Virginia State Department of Health for 3 weeks after the last possible exposure for each contact. As of December 6, no evidence of infection has appeared in any of the exposed persons. Any person with symptoms compatible with Ebola infection will be admitted to a local hospital and cared for under CDC guidelines for suspected cases of viral hemorrhagic fevers (1). Appropriate guidelines for management of newly imported primates have been sent to all U.S. primate importation and quarantine facilities, and surveillance for hemorrhagic disease in staff members and in recently imported primates is being instituted. An investigation is under way by CDC, in cooperation with foreign health officials, to identify the source of infection in the monkeys. Reported by: D Dalgard, DVM, Hazelton Research Products, Inc, Reston; JY Baumgardner, MAS, CW Armstrong, MD, SR Jenkins, VMD, CD Woolard, MPH, GB Miller, Jr, MD, State Epidemiologist, Virginia State Dept of Health. PB Jahrling, PhD, TG Ksiazekdum, PhD, EO Johnson, PhD, CJ Peters, MD, US Army Medical Research Institute of Infectious Diseases, Frederick, Maryland. Div of Quarantine, Center for Prevention Svcs; Div of Viral and Rickettsial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Unlike SHF virus, which does not cause clinical illness in humans, Ebola virus can cause severe disease in humans. This report describes the first isolation of Ebola virus in the United States.

Ebola hemorrhagic fever was first recognized in 1976, when two epidemics occurred in southern Sudan and in Zaire (2). A subsequent outbreak occurred in 1979 in Sudan (3). All three outbreaks were associated with high case-fatality rates in humans. In these epidemics, nosocomial transmission (often by contaminated needles) was followed by person-to-person transmission to household members in close contact with blood or secretions from seriously ill patients.

The ecology, natural history, and mode of transmission in nature of Ebola virus and the related Marburg virus are unknown. Before this incident, no monkey had ever been found to be naturally infected with Ebola virus. The incubation period for Ebola virus is 5-9 days (range: 2-15 days) but can be shorter with parenteral transmission. Disease onset is abrupt and characterized by severe malaise, headache, high fever, myalgia, joint pains, and sore throat. The disease course is rapid and includes pharyngitis, conjunctivitis, diarrhea, abdominal pain, and occasionally facial edema and jaundice. Severe thrombocytopenia can occur, and hemorrhagic manifestations include petechiae and frank bleeding. Death occurs primarily as a result of hypovolemic shock and its consequences. There is no specific therapy (1), and patient management is usually directed at supportive measures.

The only previous documentation of transmission of this family of virus from primates to humans occurred in 1967, when African monkeys infected with Marburg virus were imported into Europe (4). In that outbreak, human infection occurred in 25 workers handling blood and tissues from infected monkeys, and six secondary (person-to-person transmission) cases occurred; seven persons died. Animal caretakers did not become infected.

As a result of the 1967 Marburg virus outbreak, the United States and several other countries instituted a 31-day quarantine for imported monkeys. The facility in the Virginia outbreak routinely has used a 45-day quarantine. In addition to quarantine measures, the use of universal precautions in handling animals or their specimens minimizes the risk for human infections. Suspected cases of illness in potentially exposed persons should be promptly reported through state health departments to the Special Pathogens Branch, Division of Viral and Rickettsial Diseases, Center for Infectious Diseases, CDC.


  1. CDC. Management of patients with suspected viral hemorrhagic fever. MMWR 1988;37 (no. S-3):1-16.

  2. World Health Organization. Ebola hemorrhagic fever in Sudan, 1976: report of a WHO/International Study Team. Bull WHO 1978;56:247-70.

  3. Baron RC, McCormick JB, Zubeir OA. Ebola virus disease in southern Sudan: hospital dissemination and intrafamilial spread. Bull WHO 1983;61:997-1003.

  4. Martini GA, Siegert R, eds. Marburg virus disease. Berlin: Springer-Verlag, 1971.

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