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Ebola-Reston Virus Infection Among Quarantined Nonhuman Primates -- Texas, 1996

On March 30, 1996, a cynomolgus monkey (Macaca fascicularis) imported from the Philippines and held in a private quarantine facility in Texas died following a 3-day illness characterized by anorexia and lethargy. On April 11, an Ebola infection was confirmed in this animal based on antigen detection from a liver specimen as required by CDC regulation (1,2).

On April 9, a second monkey that had been held in the same room had onset of similar symptoms; this monkey was euthanized on April 13 following confirmation of Ebola infection by electron microscopy, antigen detection enzyme-linked immunosorbent assay, and reverse-transcriptase polymerase chain reaction tests of serum and blood samples. Sequence analysis of the entire glycoprotein gene of the Ebola virus from the first monkey indicated a 98.9% nucleotide identity with the original 1989 Ebola-Reston virus.

The two monkeys were part of a shipment of 100 received by the facility on March 21 and housed in two separate self-contained rooms with a capacity of 50 animals each. On April 17, the other 48 monkeys housed in the same quarantine room as the two infected animals were euthanized to minimize potential exposure of employees and to prevent additional transmission within the room. Surveillance has been enhanced for the remaining 50 monkeys and has been initiated to monitor the eight facility employees who had had contact with these monkeys. During the quarantine period, these employees had worn protective clothing and followed strict contact guidelines to minimize exposure to potential infectious agents.

Reported by: S Pearson, DVM, M Cottingham, DVM, G Pucak, DVM, HRP, Inc; K Hendricks, MD, J Taylor, MPH, G Fearnyhough, DVM, L Vela, MD, D Simpson, MD, State Epidemiologist, Texas Dept of Health. TW Geisbert, MS, PB Jahrling, PhD, US Army Medical Research Institute for Infectious Diseases, Ft. Detrick, Maryland. Div of Field Epidemiology, Epidemiology Program Office; Div of Quarantine and Special Pathogens Br, Div of Viral and Rickettsial Disease, National Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: Ebola virus is a member of a family of RNA viruses known as filoviruses. Ebola virus was discovered in 1976; since its discovery, four distinct subtypes have been identified: Zaire, Sudan, Ivory Coast, and Reston (3). Ebola-Reston subtype was discovered in the United States in 1989 in association with an outbreak of viral hemorrhagic fever among monkeys imported from the Philippines to Reston, Virginia (4). Although infection with this virus can be fatal in monkeys, the only four infections confirmed in humans were asymtomatic (5); in contrast, infection with Ebola-Sudan or Ebola-Zaire subtypes often is fatal in humans. Four additional episodes of Ebola-Reston infection among monkeys imported from the Philippines have occurred in the United States and Italy (6).

Following the earliest episodes, CDC updated and modified the mandatory disease-control requirements and other procedures used in the transportation and quarantine of nonhuman primates (1,2). The current episode in Texas indicates the importance and effectiveness of these regulations: both cases of infection were detected while the monkeys were in quarantine, and the potential for transmission to facility employees was minimal. This problem also underscores the need for further characterization of the reservoir(s) for and natural history of infection with this virus.


  1. CDC. Update: Ebola-related filovirus infection in nonhuman primates and interim guidelines for handling nonhuman primates during transit and quarantine. MMWR 1990;39:22-4,29-30.

  2. CDC. Requirement for a special permit to import cynomolgus, African green, or Rhesus monkeys in to the United States: notice. Federal Register 1990;55:15210-1.

  3. Sanchez A, Trappier SG, Mahy BWJ, Peters CJ, Nichol ST. The virion glycoproteins of Ebola virus are encoded in two reading frames and are expressed through transcriptional editing. Proc Natl Acad Sci U S A 1996;93:3602-7.

  4. Jahrling PB, Geisbert TW, Dalgard DW, et al. Preliminary report: isolation of Ebola virus from monkeys imported to USA. Lancet 1990;335:502-5.

  5. CDC. Update: filovirus infection in animal handlers. MMWR 1990;39:221.

  6. World Health Organization. Viral hemorrhagic fever in imported monkeys. Wkly Epidemiol Rec 1992;67:142.

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