Prevention of Surface-to-Human Transmission of Rotaviruses

Transcription

1 JOURNAL OF CLINICAL MICROBIOLOGY, Sept. 1991, p /91/ $02.00/0 Copyright 1991, American Society for Microbiology Vol. 29, No. 9 Prevention of Surface-to-Human Transmission of Rotaviruses by Treatment with Disinfectant Spray RICHARD L. WARD,'* DAVID I. ELIZABETH C. YOUNG,' TIMOTHY M. CUSACK,2 JOSEPH R. RUBINO,2 AND GILBERT M. SCHIFF' Division of Clinical Virology, James N. Gamble Institute of Medical Research, Cincinnati, Ohio 45219,1 and L&F Products, Montvale, New Jersey BERNSTEIN,' DOUGLAS R. KNOWLTON,' JAMES R. SHERWOOD,' Received 1 April 1991/Accepted 20 June 1991 A model was developed to examine the effects of disinfectants on the transmission of infectious rotavirus from a dried surface to humans. The initial experiments were designed to find a method of preserving rotavirus infectivity during drying. Culture-adapted human rotavirus (CJN strain) was dried at room temperature in different organic suspensions, including fecal matter, several laboratory media, and nonfat dry milk (NDM). Recoveries of infectious virus were then compared. Fecal matter provided little protection in this study relative to distilled water, but the other suspensions were quite protective, especially NDM, which consistently allowed recoveries of >50%. When 103 focus-forming units of unpassaged CJN virus were dried in NDM and administered to subjects who licked the dried material, 100% (8 of 8) became infected. The effect of Lysol brand disinfectant spray (LDS) was next examined. Although NDM provided some protection against inactivation by LDS, spraying under conditions recommended by the manufacturer consistently caused the CJN virus titer to decrease >5 loglo. Consumption of CJN virus (103 focus-forming units) sprayed with LDS caused no infection in 14 subjects, whereas 13 of 14 subjects who consumed the unsprayed virus became infected (P < ). The methods developed in this study could be used to test the effects of other disinfectants on the spread of infectious rotavirus from inanimate surfaces to humans. Rotaviruses are the primary cause of severe diarrheal disease in infants and young children (10). The transmission of rotavirus disease by the fecal-oral route could be accomplished through a variety of vehicles, including contaminated surfaces in which human hands come in contact. This route may be especially important in the documented nosocomial spread of rotavirus disease within hospitals (7-9, 15, 18, 19, 22-24) and person-to-person spread within day-care centers (3, 4, 11, 20, 21). Evidence of rotavirus contamination has been detected on the hands of workers in both settings (12, 25) as well as on inanimate objects in a day-care center (12). Furthermore, rotaviruses have been shown to survive when dried on inanimate objects (26) as well as human hands (1, 2), and fecal matter has been reported to protect the virus against inactivation in the dried state (17, 26, 35). Although the transmission of rotavirus infection by contact with the virus on a dried surface has not been documented, this is a likely route in many settings. Rotavirus could be readily transmitted from environmental surfaces either indirectly from surface to finger to mouth or directly from surface to mouth. These routes of transmission may be especially important in infants and young children, the subjects most likely to experience serious rotavirus illnesses, because they frequently place their hands on inanimate objects and in their mouths. The likelihood that the transmission of rotavirus occurs through contact with environmental surfaces is increased by the finding that fecal matter from infected infants contains 101o-1011 rotavirus particles per gram (34). Disinfection of inanimate surfaces with chemicals should inhibit the surface-to-human transmission of rotavirus infection. Such treatment incorporated into the rearing regimen of piglets has been found to limit rotavirus diarrhea (14). A * Corresponding author variety of chemical disinfectants have been tested for their abilities to prevent rotavirus infection of cultured cells; some of these appeared to be highly effective under the test conditions (16, 27, 28). The use of a disinfectant spray may be an efficient method of inhibiting the transmission of rotavirus infection, especially in settings in which these infections are endemic, such as hospital pediatric wards and day-care centers. This study was designed to determine whether the recommended use of one such disinfectant could inactivate infectious human rotavirus dried on a surface in a stabilizing medium and prevent infection of cell cultures as well as human subjects. The methods were designed as an experimental model to test the inhibitory effects of disinfectants on the surface-tohuman transmission of rotavirus infection. MATERIALS AND METHODS Virus and cells. The strain of rotavirus used in this study (CJN) was obtained from the stool of an infected child as previously described (33). This virus was adapted to grow in cell cultures by two passages in primary African green monkey kidney cells and additional passages in MA104 cells (33, 34). The virus used for in vitro studies had been passaged 36 times, including triple plaque purification on two occasions during these passages. The titer of the stock virus used for this study was 1.5 x 108 PFU/ml. The MA104 cells used to grow the virus were cultured on Dulbecco's modified minimum essential medium containing antibiotics and 10% fetal calf serum. For growth of rotavirus, flasks (175 cm2) of confluent MA104 cells were washed twice with Earle's balanced salt solution (EBSS) and inoculated with virus pretreated (1 h, room temperature) with 4,ug of trypsin per ml. After a 1-h adsorption period, Dulbecco's modified minimum essential medium with 4,ug of trypsin per ml was

2 1992 WARD ET AL. added and the flasks were rocked at 37 C until cytopathic effects were evident. Unpassaged CJN virus was obtained from the original filtered (0.2-,um-pore-size filter) stool preparation and contained 105 focus-forming units (FFU) per ml. This preparation was diluted to appropriate concentrations and used for in vivo studies with human subjects. Methods used to measure PFU (13) and FFU (5) have been described previously. Stabilization of CJN virus during drying. The stock preparation of CJN virus (1.5 x 108 PFU/ml) was mixed with equal volumes of different organic solutions or suspensions, including a 10% (wt/vol) suspension in EBSS of a stool which had no detectable neutralizing antibody to CJN virus and which was obtained from an adult subject. Small volumes (0.1 ml) were added to sterile plastic petri plates and spread evenly within a circle of a known area which had been marked on the undersides of the plates. The plates were left open within an operating biological safety cabinet, and the specimens were dried by evaporation. Specimens were visibly dry within 1 to 4 h, even when not spread. The cabinet air was constantly monitored for relative humidity and temperature throughout the time that the plates were retained by use of a recording hygrothermograph because both have been found to affect the stability of dried rotavirus suspensions (17, 26). The temperature was consistently between 24 and 28 C and the relative humidity was <50% throughout these studies. A control sample of each specimen was either frozen immediately or stored at 4 C without evaporation throughout the drying period. After different time periods, the dried specimens were resuspended by the addition of distilled water and the use of a rubber policeman and frozen at -70 C until assayed for recoverable infectious virus by plaque formation on MA104 cells. No differences in virus recoveries were observed when the dried materials were resuspended by the addition of tryptose phosphate broth or distilled water or assayed immediately without freezing or after freezing. Treatment with disinfectant. The effect of Lysol brand disinfectant spray (LDS; L&F Products, Montvale, N.J.) on CJN virus dried in 5% nonfat dry milk (NDM) was examined. LDS contains 79% ethyl alcohol, 0.1% o-phenylphenol, and CO2 propellant. The manufacturer's instructions for use of this product recommend spraying a surface for 2 to 3 s at a distance of 6 to 8 in. (ca. 15 to 20 cm) and allowing the product to stand for 10 min to air dry. For the in vitro portion of this study, CJN virus (1.5 x 10' PFU/ml) was mixed (1:1) with 10% NDM and 0.1 ml was spread in 1-, 6-, or 12-cm2 circles on petri plates and allowed to dry for 3 days in a biological safety cabinet. Dried specimens were sprayed with LDS for 3 s at distances of 8, 25, or 32 in. (ca. 20, 64, and 81 cm). During this time, 1.4, 0.5, and 0.1 g of liquid, respectively, accumulated in the 100-mm plates upon which the virus was dried. After a 10-min contact time with the lids removed from the plates, treated specimens along with untreated controls were resuspended in distilled water and assayed for recoverable PFU. Growth and purification of [3H]uridine-labeled CJN virus. MA104 cells were infected with CJN virus and labeled with [3H]uridine as previously described (30). For virus purification, frozen lysates were thawed and clarified by centrifugation (1,000 x g, 10 min). The supernatants were underlaid with CsCl (density, 1.4 g/ml) and centrifuged (SW27.1; 24,000 rpm, 90 min). The banded virus in the CsCl cushion was purified by isopycnic gradient centrifugation, and the double-shelled particles (density, 1.36 g/ml) were dialyzed against phosphate-buffered saline containing 10 mm CaCl2. J. CLIN. MICROBIOL. The purified preparation contained 2.4 x 106 cpm and 2 x 108 PFU per ml. This virus was used to monitor for recovery after different treatments. For this monitoring, the labeled preparation was mixed with various suspending media, dried, treated with LDS, and assayed for recoverable counts per minute and PFU. Route of virus transfer. The route and efficiency of transfer of CJN virus from a hard surface were examined. CJN virus in 5% NDM (0.1 ml) was spread to 6 cm2 and dried for 24 h in a biological safety cabinet. Dried virus was recovered in one of three ways. (i) Virus was transferred from plate to finger to EBSS by licking a finger, rubbing the finger directly on the dried virus spot, and swirling the finger in a known volume of EBSS. (ii) Virus was wiped with a moistened cotton sponge (to simulate a human tongue), and the sponge contents were added to a known volume of EBSS. In these two procedures, both the virus recoveries from the finger and sponge rinses as well as the quantity of infectious virus left on the plates were determined. (iii) As a control, virus was also suspended in the usual manner with distilled water and assayed for recoverable PFU. Study subjects. Participants in the study were healthy, 18- to 45-year-old males. An initial blood specimen was collected from each to determine the neutralizing antibody titer to culture-adapted CJN virus. Subjects with titers of.400 were recalled, and a general physical examination, a urinalysis, a complete blood cell count, a human immunodeficiency virus antibody determination, and a battery of blood chemistry and hematology assays were done to ensure good health status. If a subject was determined to be in good health, he was enrolled in the study. Study plan. The study protocol was approved by The Christ Hospital Institutional Review Board. Human subjects participated in two segments of this study. The first segment was conducted to determine whether dried CJN virus could infect subjects. The second segment was conducted to determine whether the transmission of infection with dried CJN virus could be prevented by treatment with LDS. In the first segment, subjects, who had been instructed to consume nothing by mouth except water for 4 h, were administered 50 ml of 4% sodium bicarbonate. These subjects (three groups of eight per group) were then administered 50 ml of EBSS containing 103 FFU of unpassaged CJN virus or consumed the same quantity of CJN virus dried in 5% NDM by either licking the dried material or transferring it to their mouths with a saliva-moistened finger. Subjects who attempted to transfer the virus with their fingers disinfected their hands with 70% ethanol both before contact with the virus and after they had sucked their fingers following viral contact. Immediately after consuming the dried virus, subjects consumed 50 ml of EBSS. All subjects were admitted to an isolation facility 2 days after the consumption of virus and remained there for 6 days. The subjects intermingled freely, but no visitors were permitted. No medication was allowed unless approved by study personnel. During isolation, participants were examined twice daily for signs and symptoms of illness. A stool was collected on the day that the virus was administered, and all stools were collected during isolation to be examined for shedding of rotavirus. Blood specimens were collected on the day that the virus was administered and 1 month later to be examined for increases in rotavirus antibody titers. Urinalysis and blood chemistry and hematology assays were repeated 1 day before subjects left the isolation facility.

3 VOL. 29, 1991 TABLE 1. Protective effects of different organic suspensions on CJN rotavirus during drying Suspending medium % Recoverable Distilled water % Stool suspension % Tryptose (Difco) Tryptose phosphate broth (Difco) % Gelatin (Difco) % NDM a After equal volumes of the culture-adapted CJN virus preparation (1.5 x 108 PFU/ml) and test medium were mixed, 0.1 ml was spread within a 6-cm2 circle on a petri plate and allowed to dry for 24 h. Recoverable PFU were then compared with those in specimens that were not dried. Determination of virus shedding. Rotavirus in stool specimens was detected by a sensitive, specific enzyme-linked immunosorbent assay as previously described (33). Determination of seroconversion. Increases in rotavirus antibody titers in serum specimens were determined by either a focus reduction neutralization assay or an enzymelinked immunosorbent assay to measure rotavirus immunoglobulin G as previously described (5, 32). Both assays have been found to be equally sensitive and, because of their high sensitivities, increases of.2-fold in both assays had been considered evidence of infection in a previous study (32). Although a -2-fold increase in rotavirus antibody titer in either assay was considered evidence of infection in the present study, the minimum increase observed in infected subjects was 3.7-fold and the maximum increase observed in uninfected subjects was 1.3-fold. Statistical analysis. Differences in outcomes were determined by Fisher's exact test. RESULTS Protection of human rotavirus during drying. Previous investigations showed that extensive inactivation of enteric viruses occurs during evaporation in water (6, 29). Fecal matter, however, may protect rotaviruses from inactivation when dried (17, 26, 35). The initial purpose of this study was to identify a suspension medium which would stabilize rotaviruses at least as well as fecal matter when dried on a plastic surface but which could also be consumed. Several organic media were analyzed for this comparative study (Table 1). Drying in NDM provided the best protection. Laboratory media were also protective, but the stool material protected viral infectivity to a much lesser extent. In fact, in some experiments, the stool material was only slightly more protective than distilled water, which yielded somewhat variable results. Extended survival of CJN virus after drying in different suspending media was next examined (Fig. 1). Again, NDM was highly protective of the virus, tryptose phosphate broth was moderately protective, but stool material provided only slight protection relative to distilled water. Loss of infectious virus in this study was not due to an inability to remove the dried virus from the plates because, when the experiment was repeated with [3H]uridine-labeled CJN virus, the recovery of radioactivity was consistently >85%, except in the specimens dried in water, for which recoveries were between 30 and 40%. These findings indicate that NDM provided excellent protection of CJN virus during and after drying. This stabi- PREVENTION OF ROTAVIRUS TRANSMISSION o 10 A C O 1 0~~~~~~~~~~~~~ Days FIG. 1. Recovery of CJN virus dried for extended times in NDM (0), tryptose phosphate broth (A), stool (O:), or distilled water (-). Specimens (0.1 ml) were spread in a 6-cm0 circle on petri plates and dried. At the times specified, they were resuspended and frozen at -70 C. The specimens collected at 2.5 h were all visibly dry. The zero-time specimens were frozen immediately without being added to the plates. PFU titers for all specimens were determined on the same date. The experiment was repeated, and the results plotted are average recoveries of duplicate experiments. lizing material was used to suspend virus prior to drying throughout the remainder of the study. Effect of NDM on inactivation of CJN virus by LDS. It was anticipated that if LDS was used to inactivate rotaviruses dried on a surface in NDM, the NDM could provide some protection. If this were true, the quantity of LDS applied could be the critical element in determining its effectiveness. Therefore, LDS was tested under conditions that both matched and were less stringent than those recommended by the manufacturer (i.e., 2 to 3 s at 6 to 8 in.). When virus was spread to 6 CM2 before being dried in NDM, a reduction in titer of 99.9% was observed after LDS treatment at 32 in., while LDS spraying at both 25 and 8 in. resulted in reductions in titers of >99.999% (Table 2). When the specimen was allowed to dry undisturbed in a compacted area (i.e., 1 CM2), LDS spraying at 32 or 25 in. caused reductions in viral recoveries of only 40 and 74%, respectively, while LDS spraying at 8 in. again reduced infectious virus titers by >99.999%. Finally, when 0.1 ml of virus was spread in NDM over a 12-cM2 circle, LDS spraying at 8, 25, or 32 in. consistently resulted in a >99.999% reduction in infectious virus titers. Therefore, the thickness of the NDM film clearly had a large effect on rotavirus inactivation with LDS, but the protective effects of the thicker films could be counteracted with larger quantities of LDS. To ensure that the observed decrease in virus titer following LDS treatment was due to inactivation and not fixation of the virus film to the plates, we determined the recovery of [3H]uridine-labeled CJN virus after LDS treatment. Over 60% of the labeled virus was recovered after LDS treatment (3 s, 25 in.) of 0.1 ml of virus spread over 6 CM2 and dried for 24 h. Thus, the loss of infectivity was not due to an inability to recover virus from the plates treated with LDS.

4 1994 WARD ET AL. TABLE 2. Effect of LDS on CJN rotavirus dried in 5% NDM Area of Recoverable PFU/ml virus spread Treatment' (%) % (CM2) 1 None 5 x 107 (100) LDS, 3 s, 32 in. 3 x 107 (60) LDS, 3 s, 25 in. 1.3 x 107 (26) LDS, 3 s, 8 in. <5 x 102 (<0.001b) 6 None 5 x 107 (100) LDS, 3 s, 32 in. 5 x 104 (0.1) LDS, 3 s, 25 in. <5 x 102 (<0.001b) LDS, 3 s, 8 in. <5 x 102 (<0.001b) 12 None 3 x 107 (100) LDS, 3 s, 32 in. <5 x 102 (<0.001b) LDS, 3 s, 25 in. <5 x 102 (<0.001b) LDS, 3 s, 9 in. <5 x 102 (<0.001b) asee Materials and Methods for conditions. b Limit of detection in cell cultures, on the basis of the cytotoxicity of LDS. Effect of route on efficiency of virus transfer in vitro. The likely routes of transmission of rotavirus include hand to hand to mouth, surface to hand to mouth, and surface to mouth. To investigate the potential role of the inanimate environment in the transfer of this virus, we developed in vitro models to examine the efficiency of transfer by the last two routes. These models measure the removal of unlabeled CJN virus dried on a surface in NDM by either a salivamoistened finger or a moistened cotton sponge as described in Materials and Methods. We presumed that licked fingers, as opposed to dry fingers, would offer the worse-case scenario in that the amount of virus removed from the surface and subsequently ingested would be maximized. When the virus was removed by licked fingers, 10 to 15% of the control amount was recovered in the EBSS rinse and 7 to 16% was found on the plate. The other 69 to 83% was not recovered because of either inactivation or virus adhesion to fingers. With the sponge method, 42 to 59% was recovered in the EBSS rinse and 1% was found on the plate. The other 40 to 57% was not recovered presumably because of either inactivation or attachment to the sponge. These results indicate that transfer of CJN virus from plate to mouth can be accomplished indirectly by touching the dried material with licked fingers or directly by licking the plate. Effect of route on efficiency of virus transfer in vivo. Before we could ascertain whether LDS treatment could interrupt the transmission of infectious rotavirus from a dried surface to humans, we needed to demonstrate that rotavirus dried in NDM could be transported to humans and cause infection. We had previously shown that unpassaged CJN virus infected approximately 75% of adults orally administered between 101 and 105 FFU of infectious virus (31, 33). The percentage of subjects becoming infected was not significantly altered by dose within this range, but subjects with high titers of rotavirus antibody were less likely to become infected than subjects with low titers (32). For protection of rotavirus from inactivation by the low ph of the stomach and to thereby maximize the sensitivity of the model, subjects were administered 4% sodium bicarbonate (50 ml) before consumption of the virus and the virus was contained in 50 ml of buffered salt solution. This same general procedure was used to test the transmissibility of CJN virus dried in NDM. Unpassaged CJN virus (103 FFU) in 5% NDM was spread TABLE 3. Effects of drying and route of inoculation on the ability of unpassaged CJN virus to infect eight subjects Inoculum No. of subjects Method of inoculation Shedding antibody With Infected rotavirusinrae increases Virus in EBSS Drinking (88) Virus dried in Licking surface (100) NDM Surface to finger (63) to mouth a Infection was defined by either shedding of rotavirus or a 22-fold increase in either serum neutralizing antibody to CJN or rotavirus immunoglobulin G as previously described (32). (0.1 ml) within 6-cm2 circles on petri plates and dried for 18 h in a biological safety cabinet. Subjects (eight each) were asked to (i) lick a plate, (ii) transfer virus from plate to mouth with a saliva-moistened finger, or (iii) drink 103 FFU of CJN virus in 50 ml of buffered salt solution (EBSS). Subjects who consumed the dried virus also drank 50 ml of EBSS immediately afterward. Although there were no significant differences in the number of subjects infected in any group, as determined by rotavirus shedding and antibody increases (P ), all eight subjects who licked the plates became infected while only five subjects who transferred virus from the plates to their mouths by their fingers became infected (Table 3). Therefore, the licking procedure was used to measure the effect of LDS on the transmission of rotavirus infection. Prevention of rotavirus infection with LDS treatment. Unpassaged CJN virus (103 FFU) dried in 5% NDM within a 6-cm2 circle on petri plates for 18 h in a biological safety cabinet was consumed by licking either 10 min after LDS treatment (3 s, 17 in. [ca. 43 cm]) or after no treatment. Plates were monitored to ensure that all visible signs of the NDM-virus mixture were removed by the subjects. Fourteen subjects were included in each group. Thirteen of those who received untreated virus became infected, but none of the subjects who consumed CJN virus after LDS treatment showed evidence of infection (Table 4). Thus, LDS treatment of infectious rotavirus dried on an inanimate surface successfully blocked the transmission of rotavirus infection to humans (P < ). DISCUSSION Because of the overall clinical significance of rotavirus and its suspected routes of transmission, this virus is a logical target for control strategies involving the use of disinfectants. The study reported here was designed as a model to measure the abilities of disinfectants to inactivate rotavi- TABLE 4. Effect of LDS on the rate of infection of 14 subjects consuming dried CJN virus No. of subjects Treatment of virus Shedding With antibody Infected rotavirus increases (%)a None (93) LDS, 3 s, 17 in (0) a Table 3, footnote a. J. CLIN. MICROBIOL.

5 VOL. 29, 1991 ruses dried on surfaces and to prevent the transmission of rotavirus infection to humans. For this model to be useful, several criteria must be met. The first is that the drying conditions must not cause extensive rotavirus inactivation. Others have shown that rotaviruses can survive for extended periods when dried in fecal matter (17, 26, 35). However, the rates of inactivation have varied considerably in different studies (17, 26). Our results indicate that merely seeding a 10% stool suspension with rotavirus provided minimal protection during drying relative to that found in distilled water. Quite possibly, the composition of specific stool specimens could have major effects on the degree of protection provided during drying, especially if they contain neutralizing antibody. Furthermore, stool material may be much less protective of seeded rotavirus than of indigenous rotavirus during drying. Thus, rotavirus naturally present in fecal matter may still be highly protected during drying. Laboratory media were found to be much more protective of rotavirus than fecal matter in this study. However, of the materials tested, NDM was the most protective. The specific properties of NDM that allowed it to be so protective during drying were not determined, but it clearly was an effective substitute for fecal matter. A second criterion to be met is that the efficacy of the disinfectant product should be known under a variety of conditions. Factors that should be considered include the protective effect of suspending media against disinfectant inactivation, the role of volume/surface area ratios in virus protection, and the effect of the amount of disinfectant applied. NDM clearly protected CJN virus, but spreading of the virus suspension over a larger area prior to drying reduced this protective effect. Thus, the protective film provided by NDM could be overcome by LDS even when used under conditions that were less stringent than those recommended by the manufacturer. To test the abilities of disinfectants to prevent the transmission of rotavirus infection to humans, a third criterion must also be met; i.e., the suspension medium must be consumable. NDM was adequate for this purpose. A final criterion is that the rotavirus tested must grow in tissue cultures so that it can be used for in vitro studies to test the virucidal effects of disinfectants. Furthermore, to be used for in vivo transmission studies, it must also infect humans. The unpassaged CJN strain of human rotavirus had been safety tested and used previously in several challenge studies without adverse effects (31-33). Because the probability of infection with this virus was found to be independent of dose over a range of 101 to 105 FFU (33), survival of only a few infectious particles after treatment with disinfectant should be sufficient to cause human infection. One of the problems inherent in testing disinfectants for their virucidal PREVENTION OF ROTAVIRUS TRANSMISSION 1995 capability in vitro is the inability to determine the complete inactivation of a virus because most disinfectants are toxic for the cell culture systems in which they are assayed. The only universal means of eliminating this cytotoxicity is through dilution, and as a result a gray zone in which the presence of virus may be masked by toxicity is created. With this model, however, the ability of disinfectants to completely inactivate the virus and prevent the transmission of rotavirus infection to humans could be quantified. The CJN virus was also amenable to in vitro studies because, after cell culture adaptation and multiple passages, it grew to a titer of >108/ml. Thus, very large numbers of infectious viruses could be seeded into suspension media before drying, and the abilities of disinfectants to reduce infectious virus titers >5 log1o could be studied. Furthermore, the culture-adapted CJN virus could be labeled with radioactive precursors, purified, and used to show that the loss of infectivity after disinfectant treatment was not due to adhesion of the virus to the surface. On the basis of the results of this study, it appears that we have developed a useful model with which to examine the transmission to humans of live rotavirus dried on nonporous, inanimate surfaces by direct or indirect contact. In addition, we have demonstrated how disinfectants may be used to interrupt this route of transmission. The virucidal properties of different disinfectants can be accurately quantified both in vitro and in vivo with this model. For this reason, it could be initially used to rapidly screen different disinfectants in in vitro studies. When the best products have been identified, the model could be used to perform the critical but much more costly human studies. Such studies could be extremely useful in identifying products that would prevent the spread of rotavirus and, possibly, other viral diseases from surfaces to humans. REFERENCES 1. Ansari, S. A., S. A. Sattar, V. S. Springthorpe, G. A. Wells, and W. Tostowaryk Rotavirus survival on human hands and transfer of infectious virus to animate and nonporous inanimate surfaces. J. Clin. Microbiol. 26: Ansari, S. A., S. A. Sattar, V. S. Springthorpe, G. A. Wells, and W. Tostowaryk In vivo protocol for testing efficacy of hand-washing agents against viruses and bacteria: experiments with rotavirus and Escherichia coli. Appi. Environ. 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