STABILITY AND INFECTIVITY OF AIRBORNE YELLOW FEVER AND RIFT VALLEY FEVER VIRUSES
ARMY BIOLOGICAL LABS FREDERICK MD
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Yellow fever virus and Rift Valley fever virus were found to be highly stable in aerosol form at temperatures of 75 F and at relative humidities of either 50 or 85 per cent. Loss of infectivity ranged between 1 and 5 per cent per minute. Yellow fever virus appeared to be more resistant to the aerosol production process than did Rift Valley fever virus although in both instances extremely potent and durable aerosols were produced. Yellow fever virus was found to be highly infective for rhesus monkeys by the respiratory route, with data indicating that less than 6 mouse ICLD50 units constituted an LD50. Both hamsters and rhesus monkeys were exposed to Rift Valley fever virus aerosols. An LD50 for hamsters of 0.5 mouse IPLD50 units was established. Monkeys were exposed to doses as low as 76 MIPLD50 units inhaled and all developed viremias with subsequent positive serology.