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.
References
CDC. Management of patients with suspected viral hemorrhagic
fever. MMWR 1988;37 (no. S-3):1-16.
World Health Organization. Ebola hemorrhagic fever in Sudan,
1976: report of a WHO/International Study Team. Bull WHO
1978;56:247-70.
Baron RC, McCormick JB, Zubeir OA. Ebola virus disease in
southern Sudan: hospital dissemination and intrafamilial spread.
Bull WHO 1983;61:997-1003.
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