Elmer W. Akin

Minimum infective dose of animal viruses

The potential for spread of viral and other infectious diseases is a function of the dose required to initiate an infection with either clinical or sub‐clinical sequelae. This is especially important for environmental spread where dilution and natural die‐off are generally assumed to play prominent roles in the control of disease. The use of disinfectants and other methods of pathogen destruction are common in certain instances but often a few survivors will eventually find routes back to their hosts. The importance of the minimum infectious dose is, therefore, evident. This report will review studies on the doses of different viruses required to initiate infection in animals and man.

Detection of viruses in water: A review of methods and application☆

Abstract One of the major problems facing environmental health officials in regard to water quality is related principally to the unavailability of reliable and standard methods to concentrate, detect, and isolate low-multiplicities of virus from very large volumes of water. The critical examination of all water supplies for the presence of viruses (including waters used for drinking, recreation, and food production) requires a quantitative approach. In order to be quantitative, measurable quantities of water must be examined. This is the only way in which a definitive assessment can be made as to the distribution and extent of virus contamination of our water resources. The challenge to the virologist is related to the need for developing new and/or improved techniques in the laboratory that have a high likelihood for adaptation to the real world situation. In this regard, a number of techniques have been shown experimentally to be good candidates for assessing the occurrence of viruses in various types of water. The most promising methods are: (i) membrane-adsorption technique; (ii) adsorption to precipitable salts, iron oxide, and polyelectrolytes; (iii) aqueous polymer two-phase separation technique; and (iv) soluble alginate filter technique. Most of these methods have shown good-to-excellent virus recovery efficiencies as well as a reasonable efficacy for concentrating viruses from water in controlled laboratory experiments. Other methods such as (i) continuous-flow ultracentrifugation; (ii) forced-flow electrophoresis and electro-osmosis, and (iii) hydroextraction have also shown favorable virus recovery efficiencies under laboratory-controlled conditions but fall short as candidate techniques for real world virus-in-water problems. From the data, it would appear that the most promising methods for detecting and isolating low-multiplicities of virus in clean and finished waters are those that rely on virus adsorption and/or retention coupled with a flow-through sampling system. For waters that are moderately or grossly turbid, it would appear that aqueous polymer two-phase separation may be the better approach. In this review paper, the above methods are briefly described in terms of mechanisms, procedure and efficiency. The methods are evaluated in terms of speed, simplicity, and economy of application.

The loss of poliovirus 1 infectivity in marine waters

Abstract The loss of infectivity (LOI) of poliovirus 1 in marine water from the Gulf of Mexico was studied. Typically, three logs of infectivity were lost in 5–6 days at 24°C. Experiments described in this report suggested that this LOI was not a result of container adsorption or virion aggregation: nor was a resistant component within the stock virus found that would have explained the two-component curves often observed with the virus loss. Viral infectivity loss occurred in raw, filter-sterilized, and autoclaved marine water. Loss was also observed when the virus was suspended in artificial seawater of 1, 10 and 20 g kg −1 salinity. No explanation for the LOI other than true inactivation of the virion was found. The specific component(s) of marine water responsible for virion inactivation remains to be ascertained.

Waterborne Viral Gastroenteritis

In studying the causes of human gastroenteritis, electron microscopy and related techniques have led to the identification of new viral agents that had previously escaped detection by routine cell culture procedures. Efforts to characterize and study these agents further are currently being made by researchers in many areas of the world. Two of the best‐known agents, rotavirus and Norwalk virus, have been implicated in waterborne outbreaks of this illness. Another virus, the Snow Mountain agent, was first identified from the investigation of one waterborne gastroenteritis outbreak.