Respiratory Infectivity of a Recently Isolated Egyptian Strain of Rift Valley Fever Virus.
ARMY MEDICAL RESEARCH INST OF INFECTIOUS DISEASES FREDERICK MD
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The respiratory infectivity of a strain of Rift Valley fever virus isolated in Egypt ZH-501 was compared to an isolate from Uganda Entebbe strain and two isolates from South Africa SA-51 and SA-75 strains. Studies were performed with ICR mice which were infected by exposure to infectious aerosols composed of particles with a mass median diameter of 0.96 micrometers. The respiratory median lethal doses for ZH-501, Entebbe, SA-51 and SA-75 were 2.2, 1.9, 2.6, and 1.9 log10 PFU, respectively, Although these values are statistically different, the biological implications of such differences seem unimportant. In an additional study of pathogenesis, a single group of mice were infected with 3.1 log10 PFU of ZH-501 and tissues were assayed sequentially through 96 h postinfection. Between 6 and 30 h, demonstration of an increasing virus concentration only in the lungs indicated that initial replication occurred there however, determination of histopathologic changes did not reveal evidence of pneumonia. Virus was isolated from the liver by 48 h, and the ultimate outcome of infection was a fulminating and fatal hepatic necrosis. Author
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