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Update: Filovirus Infection Associated with Contact with Nonhuman Primates or Their Tissues

Since November 1989, outbreaks of filovirus infection have been described among cynomolgus monkeys (Macaca fascicularis) imported from the Philippines into quarantine facilities in Virginia, Pennsylvania, and Texas (1-3). Serologic evidence of filovirus infection, including three seroconversions, among workers in these facilities (4) confirms that virus can be transmitted to humans during care and management of quarantined animals.

To further assess the health risk to humans posed by the presence of filoviruses in animals in facilities for nonhuman primates in the United States, 550 persons with varying levels of exposure to monkeys (or monkey body fluids or tissues) were tested by an indirect immunofluorescence assay (IFA) and a confirmatory Western blot assay. Of these persons, 42 (7.6%), including seven reported previously (4,5), were positive (IFA titer greater than or equal to 16, Western blot confirmed) to one or more of the four filovirus test antigens used (Ebola-Zaire, Ebola-Sudan, Filovirus-Reston, Marburg) as of June 18, 1990. Seropositivity was not evenly distributed: 26 (9.8%) of 266 import quarantine facility staff members were seropositive, and 16 (5.6%) of 284 other persons having contact with monkeys (or with monkey body fluids or tissues) outside of import quarantine facilities were seropositive. None of the 42 seropositive persons reported having had an illness considered to be caused by a filovirus.

To provide a perspective for interpreting antibody seropositivity rates for persons having contact with monkeys (or monkey body fluids or tissues), serum specimens from 449 persons from throughout the United States randomly selected from a cross-sectional adult primary-care outpatient population were tested by the same IFA and Western blot assays. Of these, 12 (2.7%) were positive. Reported by: Special Pathogens Br and Epidemiology Activity, Div of Viral and Rickettsial Diseases, Center for Infectious Diseases, CDC.

Editorial Note

Editorial Note: The filoviruses isolated in 1989 and 1990 from cynomolgus monkeys in Virginia and Pennsylvania are morphologically identical but antigenically and genetically distinct from Marburg virus isolated in Europe in 1967 (6) and Ebola virus isolated during human epidemics in Africa in the 1970s (7-10). Severe hemorrhagic fever and high death rates marked the European outbreak and the African epidemics, but human illness has not been documented in association with the recent occupationally acquired infections in the United States. Serologic data confirm that routine contact with and handling of nonhuman primates (or their body fluids or tissues) in quarantine facilities increase the risk for infection of workers. Recent actions have been taken to increase the level of worker protection during importation and import quarantine (2,11).

The background seropositivity rate for persons from throughout the United States chosen randomly from an adult primary-care outpatient population remains unexplained. One possibility is antigenic crossreactivity between the known filoviruses and another, as yet undetermined, antigen. Further investigations are in progress to clarify this. Investigations are also in progress to define risk factors for occupationally acquired infection and to assess the risk for infection of household contacts of infected persons.


  1. CDC. Ebola virus infection in imported primates--Virginia,

1989. MMWR 1989;38:831-2,837-8.

2. 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.

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

4. CDC. Update: filovirus infections among persons with occupational exposure to nonhuman primates. MMWR 1990;39:266-7,273.

5. CDC. Update: evidence of filovirus infection in an animal caretaker in a research/service facility. MMWR 1990;39:296-7.

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

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

8. World Health Organization. Ebola haemorrhagic fever in Zaire, 1976: report of an International Commission. Bull WHO 1978;56:271-93.

9. Baron RC, McCormick JB, Zubeir OA. Ebola virus disease in southern Sudan: hospital dissemination and intrafamilial spread. Bull WHO 1983;61:997-1003. 10. Gear JSS, Cassel GA, Gear AJ, et al. Outbreak of Marburg virus disease in Johannesburg. Br Med J 1975;4:489-93. 11. CDC. Requirement for a special permit to import cynomolgus, African green, or rhesus monkeys into the United States. Federal Register 1990;55:15210-1.

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