Bulletin of the World Health Organization
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Bull. World Health Organ. · Jan 1972
Isolation and properties of the causal agent of a new variola-like disease (monkeypox) in man.
The causal agent of a case of disease in man occurring in the Democratic Republic of the Congo with a similar clinical picture to smallpox was isolated and studied. The agent was identified as monkeypox virus. A comparative study of the isolated strain (Congo-8) and of viruses isolated from similar cases of illness in Liberia (Liberia-1 and Liberia-2 strains) and Sierra Leone (V-70 1 266 strain) showed that they were identical. ⋯ In 2 of the 7 sera examined, antibodies of the variola-vaccinia group of poxviruses were discovered (virus-neutralizing antibodies, precipitins, and antihaemagglutinins). In a chimpanzee, antihaemagglutinins were found in a titre of 1: 1 280, and in the same animal a variola-like virus was isolated from the kidneys. In the course of the investigation, it was shown conclusively that monkeypox virus and the strains under investigation could be distinguished from o dinary variola and vaccinia viruses on the basis of their behaviour in pig embryo kidney continuous cell line culture.
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Bull. World Health Organ. · Jan 1972
Poxviruses isolated from clinically ill and asymptomatically infected monkeys and a chimpanzee.
Poxviruses were isolated from the kidneys of an outwardly healthy chimpanzee trapped in an area of the Democratic Republic of the Congo where a case of monkeypox had recently occurred in man, from the kidneys of clinically healthy cynomolgus monkeys in a colony in the Netherlands, and from monkeys suffering from monkeypox during outbreaks in colonies in the USA. It was established that two of the three viruses isolated from animals asymptomatically infected-namely, strain Chimp-9 from the chimpanzee and strain 64-7255 from the cynomolgus monkeys-although similar to one another differed markedly from the classical Copenhagen strain of monkeypox virus. ⋯ The Chimp-9 and 64-7255 strains differed from the variola virus only in their greater pathogenicity for white mice after intracerebral inoculation. The other virus isolated from a symptomless cynomolgus monkey-strain 64-9411-resembled the two viruses isolated from monkeys suffering from monkeypox and did not differ from the Copenhagen strain.
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A poxvirus of the variola-vaccinia subgroup was isolated from the lesions of a female African refugee suffering from a smallpox-like illness. The virus is interesting because it is neither variola nor vaccinia but combines some properties of each. These properties are described and the possible origin of the virus is discussed.
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Bull. World Health Organ. · Jan 1972
Human infection with monkeypox virus: laboratory investigation of six cases in West Africa.
Between September 1970 and May 1971 six cases of human infection with monkeypox virus were identified in three West African countries-Liberia, Sierra Leone, and Nigeria. Four of the cases were confirmed by viral isolation, and two were diagnosed on epidemiological and serological evidence. ⋯ The isolated strains produced small necrotic haemorrhagic pocks on CAM, grew well at 39.0 degrees C, formed large plaques in Vero cell cultures, showed markedly more virulence for chick embryos and mice than do variola strains, and produced large necrotic haemorrhagic local lesions with generalized illness and florid secondary exanthem when inoculated into rabbit skin. The finding of smallpox-like illness in humans resulting from infection with a poxvirus of lower animal origin serves to emphasize the importance of thorough epidemiological and laboratory evaluation of all suspect smallpox cases occurring in areas where smallpox has been or is about to be eradicated.