The application of a new step for recovering poliovirus from moderately to highly turbid estuarine water by the filter virus-adsorption technique was investigated. The experiments were conducted under both (i) laboratory-based conditions (200-ml volumes) where the turbidity was controlled and (ii) simulated field conditions (15to 100-gal volumes) where the turbidity varied depending upon the hydrology of the raw estuarine water. The new step consisted of adding Celite to the turbid water prior to sampling for virus. In the experiments, the pH of the water was first adjusted to 3.5 and then AlCl3 was added to 0.0005 M. Celite was added to a concentration of 0.01% and mixed thoroughly. Either an HE Cox M-780 microfilter (Cox Instrument, Div. of Lynch Corp., Detroit, Mich.) or an MF-membrane filter (Millipore Corp., Bedford, Mass.) was used as the virus adsorbent. Virus was eluted from the Celite-filter complex in situ at pH 9 with 5x nutrient broth. In the laboratory-based experiments, when turbidity ranged from 5.0 to 30.0 Jackson turbidity units (JTU), virus recovery ranged from 66 to 89%. In the simulated field experiments, when the turbidity ranged from 8.5 to 80.0 JTU, virus recovery ranged from < 1 to 74%, depending upon the multiplicity of virus input and the level of turbidity. The new step greatly improved the filtration-flux of turbid water and significantly reduced the premature clogging problem usually observed with microporous filters.
Aerosol mixtures of the psittacosis agent, yellow fever virus, and variola virus were assayed by selective immunofluorescence in conjunction with fluorescent cell counting. The aerosol behavior of each agent could be readily delineated at test conditions of 80 F (26.67 C) and three relative humidities (30, 50, or 80%). Of the three agents, variola virus exhibited the lowest biological decay. The biological decay rates of the airborne agents were not significantly affected by humidity changes.
The effects of three temperatures [30, 50, and 80 F (-1.11, 10, and 26.67 C)] and three relative humidities (30, 50, and 80%) on biological and physical decay rates of aerosols of yellow fever virus were investigated. Neither temperature nor relative humidity, independently or jointly, significantly affected biological or physical decay rates. The advantages of assaying yellow fever virus by the fluorescent-cell counting technique are discussed. Both experimental exposure of animals (3, 5) and accidental exposure of humans (1) attest to the airborne infectivity of yellow fever virus, whose natural mode of dissemination is insect transmission (7). Knowledge of the aerosol behavior of the virus is pertinent to the evaluation of experimental infections, as well as to the prevention and control of the laboratory-acquired disease. Information on the stability of aerosols of yellow fever virus is presently limited to a few conditions of relative humidity (3, 5). Recently, a quantitative assay was developed for infective yellow fever virus particles. It is based on the enumeration of cells containing fluorescent viral antigen 24 hr after infection (2). The assay is highly precise, sensitive, in
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