Method for detecting viruses in aerosols

A simple method with poliovirus as the model was developed for recovering human enteric viruses from aerosols. Filterite filters (pore size, 0.45 micron; Filterite Corp., Timonium, Md.) moistened with glycine buffer (pH 3.5) were used for adsorbing the aerosolized virus. No virus passed the filter, even with air flow rates of 100 liters/min. Virus recovery from the filter was achieved by rapid elution with 800 ml of glycine buffer, pH 10. The virus in the primary eluate was reconcentrated by adjusting the pH to 3.5, adding AlCl3 to 0.0005 M, collecting the virus on a 0.25-micron-pore Filerite disk (diameter, 25 mm) and and eluting with 6 ml of buffer, pH 10. With this method, virus could be detected regularly in aerosols produced by flushing when 3 X 10(8) PFU of poliovirus were present in the toilet bowl. Poliovirus-containing fecal material from two of four infants who had recently received oral polio vaccine also yielded virus in the aerosols when feces containing 2.4 X 10(7) to 4.5 X 10(7) PFU of virus had been added to the toilet bowl. Persons infected with a variety of natural enteric viruses are known to excrete this amount of virus in their daily stools.     

Influence of water quality on enteric virus concentration by microporous filter methods.

Four enteric viruses, poliovirus type 1, echovirus type 1, reovirus type 3, and simian adenovirus SV-11, were concentrated from seeded 1.3-liter volumes of raw, finished, and granular activated carbon-treated waters by adsorption to 47-mm-diameter (17 cm2), electropositive ( Virosorb 1MDS ) filters at pH 7.5 or electronegative ( Filterite ) filters at pH 3.5 with and without 5 mM added MgCl2, followed by elution with 0.3% beef extract in 50 mM glycine at pH 9.5. Removal of particulates from raw and finished waters by 0.2-micron prefiltration before virus addition and pH adjustment had little effect on virus concentration efficiencies. Soluble organic compounds reduced virus adsorption efficiencies from both raw and finished waters compared with granular activated carbon-treated water, but the extent of interference varied with virus type and adsorption conditions. For electropositive 1MDS filters, organic interference was similar with all virus types. For Filterite filters, organic interference was evident with poliovirus and echovirus, but could be overcome by adding MgCl2. Reovirus and SV-11 were not adversely affected by organics during adsorption to Filterite filters. Elution of reovirus and adenovirus was inefficient compared with that of poliovirus and echovirus. None of the three adsorption schemes ( 1MDS at pH 7.5 and Filterite with and without 5 mM MgCl2 at pH 3.5) could be judged superior for all viruses and water types tested.     

Influence of water quality on enteric virus concentration by microporous filter methods

Four enteric viruses, poliovirus type 1, echovirus type 1, reovirus type 3, and simian adenovirus SV-11, were concentrated from seeded 1.3-liter volumes of raw, finished, and granular activated carbon-treated waters by adsorption to 47-mm-diameter (17 cm2), electropositive ( Virosorb 1MDS ) filters at pH 7.5 or electronegative ( Filterite ) filters at pH 3.5 with and without 5 mM added MgCl2, followed by elution with 0.3% beef extract in 50 mM glycine at pH 9.5. Removal of particulates from raw and finished waters by 0.2-micron prefiltration before virus addition and pH adjustment had little effect on virus concentration efficiencies. Soluble organic compounds reduced virus adsorption efficiencies from both raw and finished waters compared with granular activated carbon-treated water, but the extent of interference varied with virus type and adsorption conditions. For electropositive 1MDS filters, organic interference was similar with all virus types. For Filterite filters, organic interference was evident with poliovirus and echovirus, but could be overcome by adding MgCl2. Reovirus and SV-11 were not adversely affected by organics during adsorption to Filterite filters. Elution of reovirus and adenovirus was inefficient compared with that of poliovirus and echovirus. None of the three adsorption schemes ( 1MDS at pH 7.5 and Filterite with and without 5 mM MgCl2 at pH 3.5) could be judged superior for all viruses and water types tested.     

Effects of bentonite clay solids on poliovirus concentration from water by microporous filter methods.

To determine whether suspended solids interfere with enteric virus recovery from water by microporous filter methods, the effects of bentonite clay solids at a concentration of 10 nephelometric turbidity units on the recovery of poliovirus type 1 from seeded, activated carbon-treated, filtered tap water were studied. Volumes (500 ml) of virus-laden water at pH 5.5 or 7.5, with and without 50 mM MgCl2, were filtered through 47-mm-diameter, electropositive (Virosorb 1MDS) and electronegative (Filterite) filters that had been pretreated with Tween 80 to minimize direct virus adsorption to filter surfaces. Bentonite solids enhanced virus retention on both types of filters, even under conditions in which viruses were not solids associated. However, bentonite solids also interfered with elution of retained viruses when eluting with 0.3% beef extract-50 mM glycine (pH 9.5). Under some conditions, overall virus recoveries were lower from water with bentonite solids than from solids-free control water. The results of this study indicate that clay turbidity can interfere somewhat with virus recovery by current microporous filter methods.     

Poliovirus concentration from tap water with electropositive adsorbent filters.

Simple, reliable, and efficient concentration of poliovirus from tap water was obtained with two types of electropositive filter media, one of which is available in the form of a pleated cartridge filter (Virozorb 1MDS). Virus adsorption from tap water between pH 3.5 and 7.5 was more efficient with electropositive filters than with Filterite filters. Elution of adsorbed viruses was more efficient with beef extract in glycine, pH 9.5, than with glycine-NaOH, pH 11.0. In paired comparative studies, electropositive filters, with adsorption at pH 7.5 and no added polyvalent cation salts, gave less variable virus concentration efficiencies than did Filterite filters with adsorption at pH 3.5 plus added MgCl2. Recovery of poliovirus from 1,000-liter tap water volumes was approximately 30% efficient with both Virozorb 1MDS and Filterite pleated cartridge filters, but the former were much simpler to use. The virus adsorption behavior of these filters appears to be related to their surface charge properties, with more electropositive filters giving more efficient virus adsorption from tap water at higher pH levels.     

Poliovirus concentration from tap water with electropositive adsorbent filters

Simple, reliable, and efficient concentration of poliovirus from tap water was obtained with two types of electropositive filter media, one of which is available in the form of a pleated cartridge filter (Virozorb 1MDS). Virus adsorption from tap water between pH 3.5 and 7.5 was more efficient with electropositive filters than with Filterite filters. Elution of adsorbed viruses was more efficient with beef extract in glycine, pH 9.5, than with glycine-NaOH, pH 11.0. In paired comparative studies, electropositive filters, with adsorption at pH 7.5 and no added polyvalent cation salts, gave less variable virus concentration efficiencies than did Filterite filters with adsorption at pH 3.5 plus added MgCl2. Recovery of poliovirus from 1,000-liter tap water volumes was approximately 30% efficient with both Virozorb 1MDS and Filterite pleated cartridge filters, but the former were much simpler to use. The virus adsorption behavior of these filters appears to be related to their surface charge properties, with more electropositive filters giving more efficient virus adsorption from tap water at higher pH levels.     

Effects of bentonite clay solids on poliovirus concentration from water by microporous filter methods

To determine whether suspended solids interfere with enteric virus recovery from water by microporous filter methods, the effects of bentonite clay solids at a concentration of 10 nephelometric turbidity units on the recovery of poliovirus type 1 from seeded, activated carbon-treated, filtered tap water were studied. Volumes (500 ml) of virus-laden water at pH 5.5 or 7.5, with and without 50 mM MgCl2, were filtered through 47-mm-diameter, electropositive (Virosorb 1MDS) and electronegative (Filterite) filters that had been pretreated with Tween 80 to minimize direct virus adsorption to filter surfaces. Bentonite solids enhanced virus retention on both types of filters, even under conditions in which viruses were not solids associated. However, bentonite solids also interfered with elution of retained viruses when eluting with 0.3% beef extract-50 mM glycine (pH 9.5). Under some conditions, overall virus recoveries were lower from water with bentonite solids than from solids-free control water. The results of this study indicate that clay turbidity can interfere somewhat with virus recovery by current microporous filter methods.     

Effects of humic and fulvic acids on poliovirus concentration from water by microporous filtration

Because naturally occurring organic matter is thought to interfere with virus adsorption to microporous filters, humic and fulvic acids isolated from a highly colored, soft surface water were used as model organics in studies on poliovirus adsorption to and recovery from electropositive Virosorb 1MDS and electronegative Filterite filters. Solutions of activated carbon-treated tap water containing 3, 10, and 30-mg/liter concentrations of humic or fulvic acid were seeded with known amounts of poliovirus and processed with Virosorb 1MDS filters at pH 7.5 or Filterite filters at pH 3.5 (with and without 5 mM MgCl2). Organic acids caused appreciable reductions in virus adsorption and recovery efficiencies with both types of filter. Fulvic acid caused greater reductions in poliovirus recovery with Virosorb 1MDS filters than with Filterite filters. Fulvic acid interference with poliovirus recovery by Filterite filters was overcome by the presence of 5 mM MgCl2. Although humic acid reduced poliovirus recoveries by both types of filter, its greatest effect was on virus elution and recovery from Filterite filters. Single-particle analyses demonstrated MgCl2 enhancement of poliovirus association with both organic acids at pH 3.5. The mechanisms by which each organic acid reduced virus adsorption and recovery appeared to be different for each type of filter.     

Effects of humic and fulvic acids on poliovirus concentration from water by microporous filtration.

Because naturally occurring organic matter is thought to interfere with virus adsorption to microporous filters, humic and fulvic acids isolated from a highly colored, soft surface water were used as model organics in studies on poliovirus adsorption to and recovery from electropositive Virosorb 1MDS and electronegative Filterite filters. Solutions of activated carbon-treated tap water containing 3, 10, and 30-mg/liter concentrations of humic or fulvic acid were seeded with known amounts of poliovirus and processed with Virosorb 1MDS filters at pH 7.5 or Filterite filters at pH 3.5 (with and without 5 mM MgCl2). Organic acids caused appreciable reductions in virus adsorption and recovery efficiencies with both types of filter. Fulvic acid caused greater reductions in poliovirus recovery with Virosorb 1MDS filters than with Filterite filters. Fulvic acid interference with poliovirus recovery by Filterite filters was overcome by the presence of 5 mM MgCl2. Although humic acid reduced poliovirus recoveries by both types of filter, its greatest effect was on virus elution and recovery from Filterite filters. Single-particle analyses demonstrated MgCl2 enhancement of poliovirus association with both organic acids at pH 3.5. The mechanisms by which each organic acid reduced virus adsorption and recovery appeared to be different for each type of filter.     

Evaluation of the efficiency of the adsorption-elution technic for poliovirus 1 on fiber glass filters: application in the virological analysis of 100 ml to 1000 1 of water]

The efficiency of the adsorption-elution technique using fiber glass filters to concentrate viruses from water was evaluated to detect poliovirus type 1 in drinking, river, and sewage water. At pH 3.5 and with 5 X 10(-4) M aluminium chloride more than 99% were adsorbed at a 0.25-micron filter. Beef extract (3%), pH 9, eluted 85-95% of the adsorbed viruses and organic flocculation at pH 3.5 permitted to reconcentrate the viruses in 1/20 of the elution volume with a 50-72% efficiency. The overall efficiency of the technique for 100 ml to 1000 l of the different types of water using 10(2) to 10(6) PFU was 38 to 58%.     

Development of a method for concentration of rotavirus and its application to recovery of rotaviruses from estuarine waters.

As part of our studies on the ecology of human enteric viruses, an improved method for detection of rotaviruses in water was developed, and their presence in Galveston Bay was monitored. Samples (378 liters) of estuarine water adjusted to pH 3.5 and a final AlCl3 molarity of 0.001 were filtered through 25-cm pleated cartridge-type filters (Filterite Corp., Timonium, Md.) of 3.0- and 0.45-micron porosity. Adsorbed virus was eluted with 1 liter of 10% tryptose phosphate broth, pH 9.5. Primary eluates were reconcentrated to a final volume of 10 to 20 ml by a simple and rapid magnetic iron oxide adsorption and elution procedure. Two percent casein at pH 8.5 effectively eluted rotavirus from iron oxide. A total of 21 of 72 samples of water, suspended solids, fluffy sediments, and compact sediments collected in different seasons in Galveston Bay yielded rotaviruses. Recovery of rotaviruses varied from 119 to 1,000 PFU/378 liters of water, 1,200 PFU/1,000 g of compact sediment, 800 to 3,800 PFU/378 liters of fluffy sediment, and 1,800 to 4,980 PFU from suspended solids derived from 378 liters of water based on immunofluorescent foci counts on cover slip cultures of fetal monkey kidney cells.     

Development of a method for concentration of rotavirus and its application to recovery of rotaviruses from estuarine waters

As part of our studies on the ecology of human enteric viruses, an improved method for detection of rotaviruses in water was developed, and their presence in Galveston Bay was monitored. Samples (378 liters) of estuarine water adjusted to pH 3.5 and a final AlCl3 molarity of 0.001 were filtered through 25-cm pleated cartridge-type filters (Filterite Corp., Timonium, Md.) of 3.0- and 0.45-micron porosity. Adsorbed virus was eluted with 1 liter of 10% tryptose phosphate broth, pH 9.5. Primary eluates were reconcentrated to a final volume of 10 to 20 ml by a simple and rapid magnetic iron oxide adsorption and elution procedure. Two percent casein at pH 8.5 effectively eluted rotavirus from iron oxide. A total of 21 of 72 samples of water, suspended solids, fluffy sediments, and compact sediments collected in different seasons in Galveston Bay yielded rotaviruses. Recovery of rotaviruses varied from 119 to 1,000 PFU/378 liters of water, 1,200 PFU/1,000 g of compact sediment, 800 to 3,800 PFU/378 liters of fluffy sediment, and 1,800 to 4,980 PFU from suspended solids derived from 378 liters of water based on immunofluorescent foci counts on cover slip cultures of fetal monkey kidney cells.     

Round robin investigation of methods for the recovery of poliovirus from drinking water

Six laboratories actively involved in water virology research participated in a methods evaluation study, conducted under the auspices of the American Society for Testing and Materials Committee on Viruses in the Aquatic Environment, Task Force on Drinking Water. Each participant was asked to examine the Viradel (virus adsorption-elution) method with cartridge-type Filterite filters for virus adsorption and organic flocculation and aluminum hydroxide-hydroextraction for reconcentration. Virus was adsorbed to filter media at pH 3.5 and eluted with either glycine buffer (pH 10.5) or beef extract-glycine (pHG 9.0). Considerable variation was noted in the quantity of virus recovered from four 100-liter samples of dechlorinated tapwater seeded with low (350 to 860 PFU) and high (1,837 to 4,689 PFU) doses of poliovirus type 1. To have a more uniform standard of comparison, all the test samples were reassayed in one laboratory, where titers were also determined for the virus seed. Test results of the Viradel-organic flocculation method indicated that the average percentage of virus recovery for low-input experiments was 66%, with a range of 8 to 20% in two laboratories, 49 to 63% in three laboratories, and 198% in one laboratory. For the high-input experiments, two laboratories reported recoveries of 6 to 12%, and four laboratories reported recoveries of 26 to 46%. For the Viradel aluminum hydroxide-hydroextraction procedure, two laboratories recovered 9 to 11%, whereas four obtained 17 to 34% for low-input experiments. For the high-input tests, two laboratories reported a recovery of 3 to 5%, and four recovered 11 to 18% of the seeded virus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Round robin investigation of methods for the recovery of poliovirus from drinking water.

Six laboratories actively involved in water virology research participated in a methods evaluation study, conducted under the auspices of the American Society for Testing and Materials Committee on Viruses in the Aquatic Environment, Task Force on Drinking Water. Each participant was asked to examine the Viradel (virus adsorption-elution) method with cartridge-type Filterite filters for virus adsorption and organic flocculation and aluminum hydroxide-hydroextraction for reconcentration. Virus was adsorbed to filter media at pH 3.5 and eluted with either glycine buffer (pH 10.5) or beef extract-glycine (pHG 9.0). Considerable variation was noted in the quantity of virus recovered from four 100-liter samples of dechlorinated tapwater seeded with low (350 to 860 PFU) and high (1,837 to 4,689 PFU) doses of poliovirus type 1. To have a more uniform standard of comparison, all the test samples were reassayed in one laboratory, where titers were also determined for the virus seed. Test results of the Viradel-organic flocculation method indicated that the average percentage of virus recovery for low-input experiments was 66%, with a range of 8 to 20% in two laboratories, 49 to 63% in three laboratories, and 198% in one laboratory. For the high-input experiments, two laboratories reported recoveries of 6 to 12%, and four laboratories reported recoveries of 26 to 46%. For the Viradel aluminum hydroxide-hydroextraction procedure, two laboratories recovered 9 to 11%, whereas four obtained 17 to 34% for low-input experiments. For the high-input tests, two laboratories reported a recovery of 3 to 5%, and four recovered 11 to 18% of the seeded virus.(ABSTRACT TRUNCATED AT 250 WORDS)     

Novel approach for modifying microporous filters for virus concentration from water.

Electronegative microporous filters composed of epoxyfiberglass (Filterite) were treated with cationic polymers to enhance their virus-adsorbing properties. This novel and inexpensive approach to microporous filter modification entails soaking filters in an aqueous solution of a cationic polymer such as polyethyleneimine (PEI) for 2 h at room temperature and then allowing the filters to air dry overnight on absorbent paper towels. PEI-treated filters were evaluated for coliphage (MS2, T2, and phi X174) and enterovirus (poliovirus type 1 and coxsackievirus type B5) adsorption from buffer at pH 3.5 to 9.0 and for indigenous coliphages from unchlorinated secondary effluent at ambient pH. Adsorbed viruses were recovered with 3% beef extract (pH 9). Several other cationic polymers were used to modify epoxyfiberglass filters and were evaluated for their ability to concentrate viruses from water. Zeta potentials of disrupted filter material indicated that electronegative epoxyfiberglass filters were made more electropositive when treated with cationic polymers. In general, epoxyfiberglass filters treated with cationic polymers were found to adsorb a greater percentage of coliphages and enteroviruses than were untreated filters.     

Novel approach for modifying microporous filters for virus concentration from water

Electronegative microporous filters composed of epoxyfiberglass (Filterite) were treated with cationic polymers to enhance their virus-adsorbing properties. This novel and inexpensive approach to microporous filter modification entails soaking filters in an aqueous solution of a cationic polymer such as polyethyleneimine (PEI) for 2 h at room temperature and then allowing the filters to air dry overnight on absorbent paper towels. PEI-treated filters were evaluated for coliphage (MS2, T2, and phi X174) and enterovirus (poliovirus type 1 and coxsackievirus type B5) adsorption from buffer at pH 3.5 to 9.0 and for indigenous coliphages from unchlorinated secondary effluent at ambient pH. Adsorbed viruses were recovered with 3% beef extract (pH 9). Several other cationic polymers were used to modify epoxyfiberglass filters and were evaluated for their ability to concentrate viruses from water. Zeta potentials of disrupted filter material indicated that electronegative epoxyfiberglass filters were made more electropositive when treated with cationic polymers. In general, epoxyfiberglass filters treated with cationic polymers were found to adsorb a greater percentage of coliphages and enteroviruses than were untreated filters.     

Comparison of microporous filters for concentration of viruses from wastewater.

The 1-MDS Virosorb filter and the 50S and 30S Zeta-plus filters, all with a net positive charge, were compared with the negatively charged Filterite filter for concentration of naturally occurring coliphages and animal viruses from sewage effluent. When Filterite filters were used, the effluent was adjusted to pH 3.5 and AlCl3 was added before filtration to facilitate virus adsorption. No adjustment was required with the positively charged filters. Sets of each filter type were eluted with 3% beef extract (pH 9.5) or eluted with 0.05 M glycine (pH 11.5). A maximum volume of 19 liters could be passed through 142-mm diameter Filterite filters before clogging, whereas only 11, 11, and 15 liters could be passed through the 1-MDS, 50S, and 30S filters, respectively. For equal volumes passed through the filters, coliphage recoveries were 14, 15, 18, and 37% in primary effluent and 40, 97, 50, and 46% in secondary effluent for the Filterite , 1-MDS, 50S, and 30S filters, respectively. No statistically significant difference was observed in the recovery of animal viruses among the filters from secondary effluent, whereas in the Filterite and 50S filters, higher numbers of viruses from primary effluent were recovered than in the 1-MDS and 30S filters in two of three collections. Glycine was found to be a less-efficient eluent than beef extract in the recovery of naturally occurring viruses.     

Comparison of microporous filters for concentration of viruses from wastewater

The 1-MDS Virosorb filter and the 50S and 30S Zeta-plus filters, all with a net positive charge, were compared with the negatively charged Filterite filter for concentration of naturally occurring coliphages and animal viruses from sewage effluent. When Filterite filters were used, the effluent was adjusted to pH 3.5 and AlCl3 was added before filtration to facilitate virus adsorption. No adjustment was required with the positively charged filters. Sets of each filter type were eluted with 3% beef extract (pH 9.5) or eluted with 0.05 M glycine (pH 11.5). A maximum volume of 19 liters could be passed through 142-mm diameter Filterite filters before clogging, whereas only 11, 11, and 15 liters could be passed through the 1-MDS, 50S, and 30S filters, respectively. For equal volumes passed through the filters, coliphage recoveries were 14, 15, 18, and 37% in primary effluent and 40, 97, 50, and 46% in secondary effluent for the Filterite , 1-MDS, 50S, and 30S filters, respectively. No statistically significant difference was observed in the recovery of animal viruses among the filters from secondary effluent, whereas in the Filterite and 50S filters, higher numbers of viruses from primary effluent were recovered than in the 1-MDS and 30S filters in two of three collections. Glycine was found to be a less-efficient eluent than beef extract in the recovery of naturally occurring viruses.     

The potential spread of infection caused by aerosol contamination of surfaces after flushing a domestic toilet

AIMS: To determine the level of aerosol formation and fallout within a toilet cubicle after flushing a toilet contaminated with indicator organisms at levels required to mimic pathogen shedding during infectious diarrhoea. METHODS AND RESULTS: A semisolid agar carrier containing either Serratia marcesens or MS2 bacteriophage was used to contaminate the sidewalls and bowl water of a domestic toilet to mimic the effects of soiling after an episode of acute diarrhoea. Viable counts were used to compare the numbers of Serratia adhering to the porcelain surfaces and those present in the bowl water before and after flushing the toilet. Air sampling and settle plates were used to determine the presence of bacteria or virus-laden aerosols within the toilet cubicle. After seeding there was a high level of contamination on the porcelain surfaces both under the rim and on the sides of the bowl. After a single flush there was a reduction of 2.0-3.0 log cycles cm(-2) for surface attached organisms. The number of micro-organisms in the bowl water was reduced by 2.0-3.0 log cycles ml(-1) after the first flush and following a second flush, a further reduction of c. 2.0 log cycles ml(-1) was achieved. Micro-organisms in the air were at the highest level immediately after the first flush (mean values, 1370 CFU m(-3) for Serratia and 2420 PFU m(-3) for MS2 page). Sequential flushing resulted in further distribution of micro-organisms into the air although the numbers declined after each flush. Serratia adhering to the sidewalls, as well as free-floating organisms in the toilet water, were responsible for the formation of bacterial aerosols. CONCLUSIONS: Although a single flush reduced the level of micro-organisms in the toilet bowl water when contaminated at concentrations reflecting pathogen shedding, large numbers of micro-organisms persisted on the toilet bowl surface and in the bowl water which were disseminated into the air by further flushes. SIGNIFICANCE AND IMPACT OF THE STUDY: Many individuals may be unaware of the risk of air-borne dissemination of microbes when flushing the toilet and the consequent surface contamination that may spread infection within the household, via direct surface-to-hand-to mouth contact. Some enteric viruses could persist in the air after toilet flushing and infection may be acquired after inhalation and swallowing.     

Comparison of talc-Celite and polyelectrolyte 60 in virus recovery from sewage: development of technique and experiments with poliovirus (type 1, Sabin)-contaminated multilitre samples.

For virus recovery from sewage, a mixture of talc and Celite was tested as a possible inexpensive substitute for polyelectrolyte 60 (PE 60). After adjustment of pH to 6 and the addition of 45-60 plaque forming units (PFU)/ml of poliovirus type I (Sabin) to the sewage sample under test, 100 ml of it was passed through either a PE 60 (400 mg) or a talc (300 mg)-Celite (100 mg) layer; the layer-adsorbed virus was eluted with 10 ml of 10% fetal calf serum (FCS) in saline (pH 7.2). In these experiments, PE 60 layers recovered 73-80% (mean 76%) of the input virus. In comparison, virus recoveries with the talc-Celite layers were 65-70% (mean 68%). Passage of 5 litres of raw sewage (containing 50 to 1.26 X 10(5) PFU/100 ml of the poliovirus) through the talc (15 g)-Celite (5 g) layers and virus elution with 50 ml of 10% FCS in saline gave virus recoveries of 33-63% (mean 49%). Except for pH adjustment and prefiltration through two layers of gauze to remove large solids, no other sample pretreatment was found to be necessary. Application of this technique to recovery of indigenous viruses from field samples of raw sewage and effluents has been highly satisfactory.