LETTERS TO THE EDITOR
virus? Was the virus tested to determine if it was virulent or attenuated? Attenuated live, Type 3 poliovirus is presently being used in oral immunization. If, in fact, the isolate was an attenuated form, then the primary source was probably due to human fecal contamination. However, it should be pointed out that attenuated Type 3 poliovirus may be genetically unstable and change in virulence.2 Another question that came to mind, was the leachate checked for inactivated viruses by serological methods such as ELISA or Direct FA? ELISA, for example, has been successfully used to detect viruses in other situations.3 If used in this type sampling one may be able to determine the efficiency of such landfills by sampling at varied times for active viruses as described by Sobsey' and determining inactivated forms serologically. Sobsey reported significant findings from a public health standpoint and his work appeared to have been a monumental task. However, methods as described should be investigated in order to insure adequate landfill operations which in turn would ensure the prevention of public health hazard due to enteric viruses. David L. Smalley, MS, MT(ASCP) Department of Biology Memphis State University Memphis, TN 38152
REFERENCES 1. Sobsey MD: Field survey of enteric viruses in solid waste landfill leachates. Am J Public Health 68:858-864, 1978. 2. Davis BD et al: Microbiology, 2nd Ed. Hagerstown, MD: Harper and Row, pp. 1295-12%, 1973. 3. Voller A, Bidwell D and Bartlett A: Manual of Clinical Immunology, Rose NR and Friedman H, (eds.), Washington: American Society for Microbiology, pp. 506-512, 1976.
Dr. Sobsey Responds Noting that virus-positive samples contained less than 3 coliforms per 100 ml, Mr. Smalley concludes that fecal contamination was an unlikely source for the viruses isolated. Although this is a possible explanation, there are other possible interpretations for finding low coliform levels in virus-positive samples. It is possible that the leachate 390
actually contained higher coiform levels but leachate toxicity either prevented their growth or caused them to die off. Both toxicity and die-off of coliforms due to leachates have been reported previously.'-3 If the coliform die-off rate was faster than that for enteric viruses, then the initial concentration differential between them could be reduced. Such conditions have been reported for both natural waters and treated sewage effluents.4 In response to the question about the virulence of attenuation of the isolated poliovirus, this has not been unequivocally determined. Finally, immunochemical methods were not used to search for viruses in leachates because they are not nearly as sensitive as infectivity assays for detecting infectious viruses. In the reported study, only infectious viruses were being sought because they are the only ones posing a potential public health hazard. Mark D. Sobsey, PhD Dept. of Environmental Sciences and Engineering School of Public Health University of North Carolina Chapel Hill, NC 27514
REFERENCES 1. Cameron RD and McDonald EC: Coliforms and municipal landfill leachate, Jour Water Poll Control Fed, 49:25042506, 1977. 2. Glotzbecker RA and Novello AL: Poliovirus and bacterial indicators of fecal pollution in landfill leachates, News of Environmental Research in Cincinnati, U.S. EPA, Cincinnati, OH, Jan. 31, 1975. 3. Engelbrecht, RS, Weber MJ, Amirhor P, et al: Biological properties of sanitary landfill leachate, pp. 201-216 In Virus Survival in Water and Wastewater Systems, JF Malina, Jr. and BP Sagik, (eds.), Water Resources Symposium No. 7, Center for Research in Water Resources, University of Texas, Austin, 1974. 4. Berg G and Metcalf TG: Indicators of viruses in waters, Chapter 11, pp. 267-2%, In Indicators of Viruses in Water and Food, G Berg (ed), Ann Arbor Science, Ann Arbor, MI, 1978.
Comments on Restaurant Inspections I read Dr. Kaplan's paper, published in the July 1978 issue of the Journal' which refers to our article pub-
lished in an earlier issue of the Journal.2 In it we concluded that the frequency of inspections could be adjusted according to the previous performance of the food establishment. This was not a matter of belief as alluded to by Dr. Kaplan but was based on the finding that 217 (or 78 per cent) of the 279 food establishments rated as satisfactory in September of 1974 were still so rated six months later while of the 171 establishments rated as unsatisfactory on the original inspection, only 83 (or 48 per cent) were found satisfactory six months later. Mathematical models and statistical methods such as expansion of binomials and regression and correlation analyses have often been used to estimate probabilities, predict progression of epidemics or incidence of disease, and test degrees of association. Although these models and probabilities may appear to be sophisticated and interesting to the casual observer or to a novice, they have very little value in practical life. In these years of austerity and fiscal constraints, public health administrators have to depend on professional judgment and years of experience to improve productivity and to cope with increasing demands. Among the variables which may have an impact on the findings of sanitary inspections are intermittent shortterm illness of food handlers, quality and operation of equipment, type of food served, training of food handlers, inter- and intra-individual variation among inspectors, time of day, day of week, season, and a few others. Should one take all of these variables into consideration and try to decide on an "optimum'" number of inspections per year, the proposed frequency would not only be fiscally prohibitive but, to say the least, absurd. In fact, the only way to uncover all unsanitary conditions which could lead to foodborne infection is to be present on the premises at all times. As was stated by Dr. Kaplan, "Even 30 inspections will fail to detect an unsafe condition in 4 per cent of the restaurants in which such condition exists 10 percent of the year." Assuming that available resources were unlimited, which is not the case, it would be totally wasteful to increase the number of AJPH
April 1979, Vol. 69, No. 4
LETTERS TO THE EDITOR
inspections hoping that one encounters the violations at the time of inspection. Mahfouz H. Zaki, MD, DrPH Director of Public Health Suffolk County Department ofHealth Services Hauppauge, NY 11787
REFERENCES 1. Kaplan, OB: On the effectiveness of restaurant inspection frequencies. Am J Public Health 68:670-671, 1978. 2. Zaki, M, et al: A progressive approach to the problem of food infections. Am J Public Health 67:44-49, 1977.
Dr. Kaplan's Response In their pioneering paper,' Dr. Zaki, et al, emphasized the importance of food poisoning, pointed out the inadequacies of current sanitation-scoring systems, and stated that sanitation inspection frequency "could best be determined by the compliance history of the establishment." Two objectives of my mathematical analysis were: 1. to clarify the fact that compliance history of any one establishment is not a good prediction of its future sanitation rating. A couple of inspections per year are not sufficient to categorize one establishment. However, I have no doubt that a substantial
AJPH April 1979, Vol. 69, No. 4
portion of a group of establishments which rate "satisfactory" on one inspection will also rate "'satisfactory" on the next inspection, just as Zaki, et al, found out. Indeed, on a group basis, this is a fact; 2. to suggest precisely what Zaki states in the last paragraph of his letter, i.e., inspections are not an efficient detection tool. Hence, the value of training food establishment managers (who are on the premises most of the time) is given mathematical support. Now, I must voice strong disagreements with the second and third paragraphs of Zaki's letter. Mathematical models and statistical methods are only tools. They can be used, or misused. Professionals in management science, operations research, and economics have found such tools extremely valuable, as I have. It seems incongruous that Zaki puts so much faith in professional judgment and experience: by revealing shortcomings in common inspection procedures, Zaki's paper obviously revealed flaws in many administrators' judgment and experience. Unfortunately, there is ample historical evidence that, while "experience" is useful to prevent new mistakes, it often ensures that old ones are repeated. I remain partial to mathematical analyses which can test judgmental insights.
Optimum number of inspections can be determined with a mathematical methodology I described at the APHA 1978 Convention, Operations Research Session. It consists of performing successive approximations, starting from a "'saddle point." This is the "point" at which available inspection man-hours are distributed in direct proportion to, say, low sanitation score, or high number of outbreaks, and in inverse proportion to cost of inspections. Basically, this methodology has been validated by the successful Arlington County (Virginia) inspections programs, winner of the 1978 Crumbine Award.2 Under this program, the lower the sanitation score of an establishment, the higher its inspection frequency. This program originated shortly after Zaki's paper' was published, and perhaps was inspired by it. 0. Benjamin Kaplan, PhD, MPH Dept. of Environmental Health Services San Bernardino, CA 92415
REFERENCES 1. Zaki, M. et. al. A progressive approach to the problem of food infections. Am J Public Health 67:44-49, 1977. 2. Environment and Health Committee (Single Service Institute). They're number one. Environment News Digest 44:611, 1978.
391
virus? Was the virus tested to determine if it was virulent or attenuated? Attenuated live, Type 3 poliovirus is presently being used in oral immunization. If, in fact, the isolate was an attenuated form, then the primary source was probably due to human fecal contamination. However, it should be pointed out that attenuated Type 3 poliovirus may be genetically unstable and change in virulence.2 Another question that came to mind, was the leachate checked for inactivated viruses by serological methods such as ELISA or Direct FA? ELISA, for example, has been successfully used to detect viruses in other situations.3 If used in this type sampling one may be able to determine the efficiency of such landfills by sampling at varied times for active viruses as described by Sobsey' and determining inactivated forms serologically. Sobsey reported significant findings from a public health standpoint and his work appeared to have been a monumental task. However, methods as described should be investigated in order to insure adequate landfill operations which in turn would ensure the prevention of public health hazard due to enteric viruses. David L. Smalley, MS, MT(ASCP) Department of Biology Memphis State University Memphis, TN 38152
REFERENCES 1. Sobsey MD: Field survey of enteric viruses in solid waste landfill leachates. Am J Public Health 68:858-864, 1978. 2. Davis BD et al: Microbiology, 2nd Ed. Hagerstown, MD: Harper and Row, pp. 1295-12%, 1973. 3. Voller A, Bidwell D and Bartlett A: Manual of Clinical Immunology, Rose NR and Friedman H, (eds.), Washington: American Society for Microbiology, pp. 506-512, 1976.
Dr. Sobsey Responds Noting that virus-positive samples contained less than 3 coliforms per 100 ml, Mr. Smalley concludes that fecal contamination was an unlikely source for the viruses isolated. Although this is a possible explanation, there are other possible interpretations for finding low coliform levels in virus-positive samples. It is possible that the leachate 390
actually contained higher coiform levels but leachate toxicity either prevented their growth or caused them to die off. Both toxicity and die-off of coliforms due to leachates have been reported previously.'-3 If the coliform die-off rate was faster than that for enteric viruses, then the initial concentration differential between them could be reduced. Such conditions have been reported for both natural waters and treated sewage effluents.4 In response to the question about the virulence of attenuation of the isolated poliovirus, this has not been unequivocally determined. Finally, immunochemical methods were not used to search for viruses in leachates because they are not nearly as sensitive as infectivity assays for detecting infectious viruses. In the reported study, only infectious viruses were being sought because they are the only ones posing a potential public health hazard. Mark D. Sobsey, PhD Dept. of Environmental Sciences and Engineering School of Public Health University of North Carolina Chapel Hill, NC 27514
REFERENCES 1. Cameron RD and McDonald EC: Coliforms and municipal landfill leachate, Jour Water Poll Control Fed, 49:25042506, 1977. 2. Glotzbecker RA and Novello AL: Poliovirus and bacterial indicators of fecal pollution in landfill leachates, News of Environmental Research in Cincinnati, U.S. EPA, Cincinnati, OH, Jan. 31, 1975. 3. Engelbrecht, RS, Weber MJ, Amirhor P, et al: Biological properties of sanitary landfill leachate, pp. 201-216 In Virus Survival in Water and Wastewater Systems, JF Malina, Jr. and BP Sagik, (eds.), Water Resources Symposium No. 7, Center for Research in Water Resources, University of Texas, Austin, 1974. 4. Berg G and Metcalf TG: Indicators of viruses in waters, Chapter 11, pp. 267-2%, In Indicators of Viruses in Water and Food, G Berg (ed), Ann Arbor Science, Ann Arbor, MI, 1978.
Comments on Restaurant Inspections I read Dr. Kaplan's paper, published in the July 1978 issue of the Journal' which refers to our article pub-
lished in an earlier issue of the Journal.2 In it we concluded that the frequency of inspections could be adjusted according to the previous performance of the food establishment. This was not a matter of belief as alluded to by Dr. Kaplan but was based on the finding that 217 (or 78 per cent) of the 279 food establishments rated as satisfactory in September of 1974 were still so rated six months later while of the 171 establishments rated as unsatisfactory on the original inspection, only 83 (or 48 per cent) were found satisfactory six months later. Mathematical models and statistical methods such as expansion of binomials and regression and correlation analyses have often been used to estimate probabilities, predict progression of epidemics or incidence of disease, and test degrees of association. Although these models and probabilities may appear to be sophisticated and interesting to the casual observer or to a novice, they have very little value in practical life. In these years of austerity and fiscal constraints, public health administrators have to depend on professional judgment and years of experience to improve productivity and to cope with increasing demands. Among the variables which may have an impact on the findings of sanitary inspections are intermittent shortterm illness of food handlers, quality and operation of equipment, type of food served, training of food handlers, inter- and intra-individual variation among inspectors, time of day, day of week, season, and a few others. Should one take all of these variables into consideration and try to decide on an "optimum'" number of inspections per year, the proposed frequency would not only be fiscally prohibitive but, to say the least, absurd. In fact, the only way to uncover all unsanitary conditions which could lead to foodborne infection is to be present on the premises at all times. As was stated by Dr. Kaplan, "Even 30 inspections will fail to detect an unsafe condition in 4 per cent of the restaurants in which such condition exists 10 percent of the year." Assuming that available resources were unlimited, which is not the case, it would be totally wasteful to increase the number of AJPH
April 1979, Vol. 69, No. 4
LETTERS TO THE EDITOR
inspections hoping that one encounters the violations at the time of inspection. Mahfouz H. Zaki, MD, DrPH Director of Public Health Suffolk County Department ofHealth Services Hauppauge, NY 11787
REFERENCES 1. Kaplan, OB: On the effectiveness of restaurant inspection frequencies. Am J Public Health 68:670-671, 1978. 2. Zaki, M, et al: A progressive approach to the problem of food infections. Am J Public Health 67:44-49, 1977.
Dr. Kaplan's Response In their pioneering paper,' Dr. Zaki, et al, emphasized the importance of food poisoning, pointed out the inadequacies of current sanitation-scoring systems, and stated that sanitation inspection frequency "could best be determined by the compliance history of the establishment." Two objectives of my mathematical analysis were: 1. to clarify the fact that compliance history of any one establishment is not a good prediction of its future sanitation rating. A couple of inspections per year are not sufficient to categorize one establishment. However, I have no doubt that a substantial
AJPH April 1979, Vol. 69, No. 4
portion of a group of establishments which rate "satisfactory" on one inspection will also rate "'satisfactory" on the next inspection, just as Zaki, et al, found out. Indeed, on a group basis, this is a fact; 2. to suggest precisely what Zaki states in the last paragraph of his letter, i.e., inspections are not an efficient detection tool. Hence, the value of training food establishment managers (who are on the premises most of the time) is given mathematical support. Now, I must voice strong disagreements with the second and third paragraphs of Zaki's letter. Mathematical models and statistical methods are only tools. They can be used, or misused. Professionals in management science, operations research, and economics have found such tools extremely valuable, as I have. It seems incongruous that Zaki puts so much faith in professional judgment and experience: by revealing shortcomings in common inspection procedures, Zaki's paper obviously revealed flaws in many administrators' judgment and experience. Unfortunately, there is ample historical evidence that, while "experience" is useful to prevent new mistakes, it often ensures that old ones are repeated. I remain partial to mathematical analyses which can test judgmental insights.
Optimum number of inspections can be determined with a mathematical methodology I described at the APHA 1978 Convention, Operations Research Session. It consists of performing successive approximations, starting from a "'saddle point." This is the "point" at which available inspection man-hours are distributed in direct proportion to, say, low sanitation score, or high number of outbreaks, and in inverse proportion to cost of inspections. Basically, this methodology has been validated by the successful Arlington County (Virginia) inspections programs, winner of the 1978 Crumbine Award.2 Under this program, the lower the sanitation score of an establishment, the higher its inspection frequency. This program originated shortly after Zaki's paper' was published, and perhaps was inspired by it. 0. Benjamin Kaplan, PhD, MPH Dept. of Environmental Health Services San Bernardino, CA 92415
REFERENCES 1. Zaki, M. et. al. A progressive approach to the problem of food infections. Am J Public Health 67:44-49, 1977. 2. Environment and Health Committee (Single Service Institute). They're number one. Environment News Digest 44:611, 1978.
391
