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The need for a home hygiene policy and guidelines on home hygiene An Ad Hoc Meeting of the International Scientific Forum on Home Hygiene* Date 1997 *The International Scientific Forum on Home Hygiene currently comprises: Dr Rijkelt Beumer Vakgroep Levensmiddlentechnologie, Universitaet van Wageningen, Wageningen, The Netherlands Professor Sally Bloomfield International Hygiene Research and Liaison Manager, Unilever Research, Port Sunlight, UK and Professor of Environmental Health, Division of Life Sciences, King’s College London, London, UK Professor Dr Martin Exner Direktor, Hygiene-Institut, Rheinische Friedrich-Wilhelms-Universität, Bonn, Germany Professor Gaetano Fara Direttore dell’Istituto di Igiene “G. Sanarelli”, Università “La Sapienza” di Roma, Rome, Italy Dr Elizabeth Scott Consultant in Food and Environmental Hygiene, Newton, Massachusetts, USA CONTENTS Introduction What do we mean by home hygiene? The need for a home hygiene policy The increasing incidence of food-borne diseases acquired in the home environment The emergence of new pathogens and their significance in the home Implications of the risk of domestically acquired infections in susceptible groups The home healthcare environment The threat posed by the continuing increase in resistance to antibiotics in clinical practice Education and public awareness A proposal for establishing guidelines on home hygiene The development of home hygiene guidelines based on risk assessment 1. 2. 3. 4. Infection potential of sites and surface in the home Infection and cross contamination routes within the domestic environment Home environment factors Groups who may particularly benefit from hygiene guidelines and education Infection prevention and improving hygiene in the home Advice on appropriate decontamination processes in the home Summary and conclusions References INTRODUCTION Currently there would appear to be relatively little concern amongst government authorities regarding the importance of home hygiene in the prevention of community-based infections. This may be for a number of reasons, including prevailing attitudes to infection control, a focus on hospital, institutional and food manufacturing hygiene, and the relative lack of epidemiological data and under-reporting of infections related to the home environment. Furthermore, there is currently no recognised organisation that takes responsibility for this area of concern. However, there are a number of reasons to suggest that awareness of home hygiene and its contribution to family health should, as a matter of urgency, be given higher priority in the development of national and global healthcare policies. For example, there is considerable evidence that the incidence of food-borne illnesses in Europe is increasing, with many of these infections now recognised to be acquired in the home. The emergence of new pathogens such as E. coli H7:O157 and of antibiotic resistant bacteria has recently received considerable attention, although the significance of E. coli H7:O157 in relation to domestic food preparation, and the potential risk from methicillin resistant Staphylococcus aureus (MRSA) in the home environment, has to date been given little consideration. It has been cited that public education on preventing the spread of E. coli H7:O157 within the home would reduce the burden of this infection (Parry et al. 1998). Furthermore, changing trends in healthcare mean that more people, including the elderly, are now being nursed or cared for in a home healthcare environment. These factors, combined with evidence showing that the public have a poor understanding of microbiological risk, proper food storage and preparation procedures and awareness of home health hazards, suggest that raised awareness of the need for good home hygiene and better education of the public on good hygiene practice could contribute to a more healthy home environment. At an international meeting of experts with an interest in hygiene, various issues were reviewed. A strategy was agreed for the development of “Guidelines for Home Hygiene” which would give a comprehensive and cohesive approach to all aspects of hygiene in the home. The consensus view from this meeting is summarised in the following paper. What do we mean by Home Hygiene? At the present time, if we talk about “home hygiene”, we tend to be referring to the general day to day cleaning of the home. In practice, home hygiene encompasses something much wider. Micro-organisms are introduced continually into the home in a number of ways - on people, food, pets, insects and via water. In addition certain areas or sites in the home environment where stagnant water and organic residues accumulate such as sinks, sink and basin U-tubes, toilets, wet cleaning cloths and facecloths, readily support the growth of potentially pathogenic species and can thus become a primary source or reservoir of infection. Many of the types of organisms which enter or reside in the home are of little consequence and some can be actually beneficial. Some organisms, however, have the potential to cause infectious disease, although even for these species contact with small numbers of organisms is known to be important in maintaining the immune system of the normal healthy adult. The fact that potentially harmful organisms can cause an infection in one person within the household (most usually someone within a vulnerable group e.g. a neonate) but not others is a further complication. Some people may also carry highly pathogenic organisms and bring them into the home, without themselves being affected so that other family members are entirely unaware of the hazard. Home hygiene is the sum total of the measures used to prevent infection and the transfer of infection within the home environment. These measures may be categorised into four main areas, namely food hygiene, personal hygiene, general home hygiene, and home “healthcare”. Home healthcare (i.e. infection control in the home as opposed to hospital infection control) includes specific situations of perceived or increased risk such as care of neonates and geriatrics, infection control measures associated with home nursing of immune-compromised family members, and infection control measures associated with family members who are carriers of HIV or MRSA. It also includes situations where decontamination of faecal or other “spillage” material from neonates or pets, for example, is required. Procedures such as disinfection of contact lenses must also be regarded as routine home healthcare. THE NEED FOR A HOME HYGIENE POLICY As stated at the outset there are a number of issues, supported by epidemiological and microbiological data, which suggest the need for an improvement in home hygiene awareness and home hygiene practices: The increasing incidence of food-borne diseases acquired in the home environment There is considerable evidence that the incidence of food-borne disease is increasing in Europe. The most accurate data available are provided by the UK and the Netherlands, which have effective surveillance and data collection systems. In the UK there has been a significant increase over 10 years to almost 100,000 cases in England and Wales in 1997, compared with 70,000 cases in 1992. This figure is considered to be an underestimate since only a fraction of cases are reported to a doctor. Surveys completed in the Netherlands are thought to give a more accurate figure of 2.5 million gastroenteritis cases per year in contrast to the 300 per year identified by the data collection system (Hoogenboom-Verdegaal 1994). Data from surveillance programmes in various European countries and the USA, as reviewed by Scott (1996), is variable in quality but indicates that in most countries there is a significant problem. In contrast to the prevailing view of the public that food-borne infections are acquired in establishments such as restaurants, data from a number of countries indicate that many outbreaks of food-borne disease originate in the home. This misconception may arise because large outbreaks of food-borne illness due to problems in food manufacturing and food service facilities are more likely to be reported to public health authorities and to receive subsequent attention by the media and the public than smaller outbreaks resulting from poor hygiene in the home (Knabel et al. 1995). Estimates from the UK by Sheard (1986) covering the period 1980 to 1986 suggest that private homes account for more outbreaks than the sum total of other reported locations. A more recent study (Ryan et al. 1996) covering the period 1992 to 1994 indicated that 16% of food poisoning outbreaks occurred in the domestic setting, although it was suggested that this figure is an underestimate. Data from the Netherlands indicates that as much as 80% of sporadic Salmonella and Campylobacter infections arise in the home (Hoogenboom-Vergdegal and Postema 1990) whilst data from Spain shows the private home as the location of up to 50% of all outbreaks. A recent study in Italy (Scuderi et al. 1996) showed that 74% of Salmonella outbreaks were associated with the home. A similar survey in the US (Aserkoff et al. 1970) indicates that the largest proportion of food poisoning outbreaks originate in the home. There are a number of reasons that may explain the increasing incidence of gastrointestinal infections associated with the home environment, including changes in technology/husbandry of commercial food production, deficiencies in slaughterhouse practices, changes in domestic practices of food preparation and eating habits, and increasing preference for fresh rather than preserved foods. The emergence of new pathogens and their significance in the home The ongoing emergence of new pathogens represents a serious global problem (Anon 1996). Many emerging infections are caused by species which are normally present in the environment but which hitherto have had little clinical impact on man. The increased clinical significance of these species relates to a number of factors such as changing environmental conditions and deficiencies in the prevention and control of infectious diseases (Morse 1995). Several of these species are now emerging as important foodborne pathogens such as E. coli O157:H7, Campylobacter jejuni, Listeria monocytogenes, Vibrio cholera O139, Norwalk virus and Yersinia enterocolitica (Lederberg, Shope and Oaks 1992; Doyle 1991) all of which may have an impact on home health unless emphasis on preventive practices is highlighted. Certain pathogens (e.g. HBV, Helicobacter pylori) are also now implicated as the cause of or as cofactors in cancer and possibly of chronic degenerative diseases (Anon 1996). Implications of the risk of domestically acquired infections in susceptible groups Alternatively, a microbial species may emerge as a pathogen because of changes in host susceptibility to infection (Morris 1997). Factors which lead to increased susceptibility to infection within a population include increased numbers of immune-compromised patients, increased use of immunosuppresssive agents, ageing of the population and use of drugs such as antibiotics, all of which have an impact in the home. As the population structure of Europe ages, infection risk in the home and its consequences can be expected to increase. It has been estimated that approximately 20% of the population (neonates, geriatrics, pregnant mothers, immune-compromised patients discharged into the community) may be classified within a high-risk or “at risk” group, whose immune defences against infection can be expected to be less than that associated with the normal healthy adult and who therefore require additional guidance on hygiene and hygiene precautions (Gerba, Rose and Haas 1996). For most people the quality of their life (their health expectancy) is at least as important as their life expectancy. It is generally accepted that the infection risk in the general community is less than that associated with patients in hospitals. Although the levels of pathogenic organisms found at some sites within the home may be relatively low, it has been suggested that, for susceptible groups, these levels may still represent a particular risk in susceptible groups (Scott 1996). For people such as the elderly, with high susceptibility to infection, the clinical sequelae of food-borne disease in these groups can have severe consequences. The home healthcare environment Due to changing trends in healthcare, increasing numbers of sick people are now being cared for at home. These, as mentioned above, may be patients with immune compromising conditions. This can be associated with a range of conditions including not only patients using immunosuppressant drugs but also those using invasive systems (indwelling catheters) or inhalation systems or devices. The number of otherwise healthy family members with asthma or allergies, another condition associated with increased susceptibility to infection, is increasing. Other patients now frequently cared for in the community include those suffering from communicable diseases such as HIV or carrying an antibiotic resistant pathogen such as MRSA, which represent a threat to other family members. A recent investigation of the domestic environment occupied by a nurse known to be colonised with MRSA revealed contamination on door handles, a computer desk shelf and computer joystick (Masterton et al. 1995). Family members involved in home healthcare often do not understand basic infection prevention measures and require education on correct procedures. By providing home caregivers and other healthcare providers who work in the home with hygiene guidance it should be possible to reduce the risk of infection to both patients and caregivers (Simmons et al. 1990). The threat posed by the continuing increase in resistance to antibiotics in clinical practice Antibiotic resistance is now considered as a major health threat (Anon 1997). The implication from this is that greater emphasis must now be placed on preventive hygiene practices rather than reliance on antibiotic therapy. Although antibiotic resistance has largely been considered as a hospital-based problem, control of resistant strains such as MRSA is now a community as well as a hospital problem (Wagenvoort et al. 1997). Experience is now showing that rigorous implementation of infection control measures (i.e. good hygiene) with reduced antibiotic usage can have a significant impact in reducing antibiotic resistance (Anon 1997). Education and public awareness Two recent questionnaire studies in the United States have raised concern over the inadequate consumer knowledge of foodborne microbial hazards, food-handling practices and their misconceptions regarding the sources and consequences of foodborne illness (Fein, Lin and Levy 1995; Altekruse et al. 1995). Patterns of home food preparation are also changing in Europe and the United States. It is no longer the case that one person is responsible for food preparation. Now children and other adult household members are all involved in food preparation or food handling - more food handlers need to be educated and the information to be conveyed is increasingly complex (Wolf 1995). A PROPOSAL FOR ESTABLISHING GUIDELINES ON HOME HYGIENE Overall the evidence suggests that comprehensive guidelines on all aspects of home hygiene would be a valuable aid in educating hygiene professionals (i.e. those people whose job or profession involves advising the public on hygiene and healthcare), and ultimately the public, on microbiological risk in the home environment and the way in which this risk might be reduced through improvements in home hygiene. As stated previously micro-organisms are introduced continually into the home - in a number of ways - on people, food, pets and via water. These must be considered as the primary sources of potentially harmful micro-organisms in the home. In addition certain areas or sites in the home environment where stagnant water and organic residues accumulate, such as sinks, sink and basin U-tubes, toilets, wet cleaning cloths and facecloths, will readily support the growth of potentially pathogenic species and thus also become a primary source or reservoir of infection. Currently, many aspects of hygiene which relate to the domestic environment tend to be compartmentalised into recognised areas such as advice on food hygiene, advice on personal hygiene, or what to do if there is a young baby in the home. Since all of the appropriate hygiene activities are based on the same underlying microbiological principles, it is more appropriate that they are discussed together and advice on all areas of hygiene relevant to the home provided. Although a significant proportion of infections occur as the result of person to person contact and can only be controlled by changes in social behaviour, indications are that many infections relate to poor hygiene and could be prevented by proper infection control procedures. The main principles for optimising infection control in any environment are concerned with: the reduction or elimination, where feasible, of sources/reservoirs of infection preventing transfer of contamination from these sources In the home, as far as food is concerned, the main emphasis is on elimination of the contaminating organisms to a safe level by application of a cooking process. However, preventing transfer of contamination during the cooking and food preparation processes is also extremely important. As far as other primary sources are concerned, namely people and pets, elimination is not an option! Thus, the major emphasis is on prevention of transfer which involves good surface hygiene (mainly hands and hand contact surfaces). For environmental reservoirs of infection, experience has shown that, since in many situations there is continual recontamination of surfaces or sites either due to recontamination or re-growth of residual survivors, elimination of risk organisms is not a feasible proposition (Scott, Bloomfield and Barlow 1984). The emphasis for controlling infection from these sites is again on managing these risks through appropriate hygiene practices which prevent infection transfer. The implied purpose of applying a hygiene procedure anywhere in the home, as elsewhere e.g. in hospitals, is to achieve a reduction in the number of viable organisms to a level where there is no longer a threat to health. One of the problems of drawing up guidelines for good hygiene however is that the level of risk from exposure to micro-organisms is variable according to specific circumstances. Cross infection in the domestic environment does not always result in an infectious disease; the risk of infectious disease arising from transfer of infection in the domestic environment is highly variable and depends on a number of factors: The presence and pathogenicity of the organism The infective dose - there is a direct correlation between the size of the infecting dose and the risk of infection The susceptibility of the host. Neonates, geriatrics, pregnant mothers and other immunocompromised people are at increased risk of infection. Even for healthy adults, susceptibility to infection can be altered by various factors e.g. stress, alcohol use, and even the use of medications such as antacids which reduce the effectiveness of the acid barrier The route by which the organism enters the body e.g. oral, topical etc. The degree of occupancy of the home and the climatic conditions. This variability demands that a “flexible approach” is adopted according to each specific situation or problem. This can only be achieved by a proper awareness of these interdependent factors (Scott 1996) which in turn depends on sound education; as with any educational programme, members of the public are unlikely to achieve improvements in home hygiene unless they understand which practices in the home are most likely to contribute to the infection risk and the factors which increase or decrease the risk. Such information must be incorporated into the guidelines and, ideally also, explained. In order to identify potential health hazards, it is proposed that guideline advice should be based on identifying critical control points in the home using risk analysis approaches. The use of hazard analysis and critical control point (HACCP) evaluation in identifying areas of potential risk in certain food manufacturing processes is well documented and a recognised tool for analysing critical factors which may lead to food contamination or infection risk and for introducing control measures. Griffith and Worsfold (1994) suggested that HACCP has a role in the preparation of food in the domestic environment, with potential applications in forming the basis of health-education programmes to improve consumer awareness of food-borne disease and its prevention. The application of HACCP to other aspects of home, apart from not only food preparation procedures, is also proposed as a valuable way of identifying risks associated with particular home situations, for example, when there is a young child, an elderly person or someone with an infection resident in the home (Jones 1997). THE Development of HOME HYGIENE GUIDELINES BASED ON RISK ASSESSMENT In developing guidelines for home hygiene based on a risk assessment approach a number of factors need to be taken into account: 1. Infection potential of sites and surface in the home A review of microbial contamination of the home enables us to identify sites and surfaces most likely to contribute to infection risk. Several published studies have shown that a wide range of potentially pathogenic micro-organisms are commonly found at sites in the home (Finch et al. 1978; Scott, Bloomfield and Barlow 1982), with the most commonly identified sites being the kitchen and bathroom. A microbiological survey of the home by Scott et al. (1982) reported the presence of pathogenic bacteria and opportunistic pathogens in reservoir sites such as kitchen sinks and at contact transfer sites in the kitchen and bathroom. A similar pattern was reported by Finch et al. (1978), and more recently by Josephson et al. (1997). In a survey of 213 homes, Listeria species were found in about 15% of homes and were recovered from wet sites such as the kitchen sink, dishcloths and washing up brushes, the refrigerator and the toothbrush (Beumer et al. 1996). The species of Enterobacteriacae isolated in these various studies included Klebsiella, Enterobacter, Citrobacter, Proteus and E. coli. Although these species are not normally pathogenic to the healthy adult, they must be regarded as indicators of poor hygiene. Species of Pseudomonas (including Ps. aeruginosa) and Staph. aureus were also isolated. The fact that in all of these studies primary pathogens such as Salmonella was isolated only once and Campylobacter only twice (Josephson et al. 1997) should not be taken as an indication that environmental transfer of these pathogens is not a problem; it must be borne in mind that the number of homes surveyed was relatively small in global terms, and the homes were evaluated under “normal” conditions i.e. not specifically during or immediately after food preparation, or where there was a known carrier. Van Schothurst et al. (1978) demonstrated that, in 73 homes where a case of salmonellosis had occurred, in over half of these homes, isolates of the same serotype were isolated from environmental sites including worktops, sinks, towels etc. De Wit et al. (1979) demonstrated the potential for cross-contamination via inanimate surfaces in the home during preparation of raw chickens, whilst Humphrey et al. (1994) showed recovery of Salmonella enteritidis PT4 from fingers and utensils, sometimes after washing, following preparation of egg dishes using artificially contaminated eggs. In the latter study the organisms could be recovered from dry films of batter or eggs on work-surfaces up to 24h after contamination. Most usually pathogens found in the home are brought in on raw or processed food contaminated, with the micro-organisms most commonly implicated in food-poisoning cases including Salmonella, Campylobacter and Listeria. Micro-organisms are ubiquitous throughout nature and can often contaminate raw agricultural food products. Levels of contamination in raw products are reduced by treatment and preservation processes, but will survive, and humans may re-contaminate foods during production, processing, distribution or preparation. Any food, therefore, whether raw or processed may carry some level of risk for foodborne illness if not properly handled in the home before consumption (Knabel et al. 1995). During and after viral infections, virus particles may be shed in large numbers in many body fluids including blood, faeces, saliva, urine and nasal secretions. There are a number of laboratory investigations which indicate that viral species including rotavirus, rhinovirus, adenovirus, poliovirus, herpes simplex virus and hepatitis A virus can survive for significant periods on dry surfaces (Mahl and Sadler 1975; Nerukar et al. 1983; Sattar 1986; Ansari et al. 1988; Ward et al. 1991; Mbithi et al. 1991) but no studies have been carried out to investigate the prevalence of viral species at environmental sites and surface in the home environment. The risk of young pets bringing potentially infectious organisms into the home is also recognised. High levels of contamination on the paws of dogs and cats have been found and it has been concluded for example that dogs may serve as a source of salmonellosis, especially in children (Morse et al. 1976; Wall et al. 1996). 2. Infection and cross contamination routes within the domestic environment Another factor which needs to be taken into account is the fact that the risks associated with environmental contamination depend not only on whether the site is contaminated, but also the probability of transfer - either to food, to other surfaces, or directly from hand to mouth. For example, a surface contaminated with Salmonella may be a hazard but only becomes a health risk if those micro-organisms are transferred from that surface either to the person or to food, and if the numbers transferred, or eaten, exceed an infective dose. The majority of food poisoning cases result from the consumption of contaminated food. Considerable research has been performed on identifying the actual causes for food-borne disease outbreaks. Identified steps include preparation of food too far in advance which enables contamination of products and the growth of micro-organisms to levels responsible for clinical disease (Roberts 1982). An interval of more than 12 hours between preparation and eating, improper cooling and inadequate re-heating have been identified as the most important causes of contaminated food outbreaks (Bryan 1988). Guidelines on home hygiene must therefore give clear guidance on methods for cooking and storage of foods and need to be communicated to the consumer in health education campaigns. The importance of good food hygiene in the home cannot be underestimated. Cross-contamination during food preparation has been identified as a common cause of food poisoning and can occur at any stage in food preparation (Foulger 1980). Sources of contact transfer sites include food preparation surfaces and the occurrence and survival of bacteria and viruses on such surfaces has been well documented. Wet cloths, cleaning utensils, together with hand and food contact surfaces are important elements in cross-contamination (Scott and Bloomfield 1990). Where contaminated surfaces or cloths containing even relatively low levels of bacteria come into contact with fingers or surfaces, organisms may be transferred in sufficient numbers to represent a potential infection hazard (Scott and Bloomfield 1990). Reviewing the mechanisms of transmission of food-borne infection Roberts (1990) concluded that, although most outbreaks result from poor temperature control of raw and cooked foods, a significant number are directly or indirectly associated with cross-contamination, although crosscontamination via surfaces is relatively less frequent. Data suggest that cross-contamination is implicated in about 6%, and poor hand hygiene in about 4%, of outbreaks. Roberts (1986) reported that cross-contamination was a contributory factor in 14% of UK outbreaks of human salmonellosis. A more recent UK study of food poisoning (1992-1994) outbreaks in the domestic setting suggested that cross contamination was a contributory factor in 28% of the outbreaks investigated. The importance of the hands as a means of transfer not only of food poisoning bacteria but also other pathogenic species, is well accepted, such that the need for good hand hygiene is usually well emphasised in hygiene education literature and hygiene education campaigns. There are a number of reports in the literature in which the circumstantial evidence strongly suggests direct hand to mouth transfer as the cause of food poisoning. Although consumption of contaminated, undercooked beef products accounts for most outbreaks of E. coli O157:H7, other food vehicles are also responsible for transmission and improper hygiene with secondary spread from person-toperson contact is another well-documented route of infection (Feng 1996; Griffin and Tauxe 1991). The CDC report that many unrecognised, sporadic outbreaks of E. coli O157:H7 probably occur in the US due to undercooking of meat products, such as hamburgers, in the home (Anon 1994a; Knabel et al. 1995). Although hand transfer of infection is well accepted, there is some reluctance to accept that inanimate surfaces may can represent the route of transfer for a range of different infectious diseases, not only in the hospital environment but also in the home. During the 1970s and 1980s Maki et al. (1980) and McGowan (1981) reported microbiological surveillance studies of hospitals showing that, although control procedures could be used to reduce the incidence of contamination in the hospital environment, there was no evidence of any reduction in the incidence of infection. These results have encouraged the belief that general environmental sites and surfaces do not represent a hazard, which is not the case. From time to time infection outbreaks (hospital, institutional and domestic) involving a variety of bacteria and fungal species are reported in the literature in which environmental sites and surfaces are cited as the source or means of transfer (Bloomfield and Scott 1997). Although such reports are infrequent they illustrate the potential for infection transfer involving direct contact with inanimate surfaces. Indications are that Shigella sonnei infection usually spreads from person to person and is associated with poor personal hygiene/toilet facilities. Shigella infection is also facilitated in schools and day-care centres by handling contaminated toys and other inanimate objects. The infectious dose is very small and young children are implicated in the spread of shigellosis to their families (Evans and Maguire 1996). Rotaviruses are the primary cause of severe diarrhoeal disease in infants and young children and faecal-oral transmission may occur via hand contact with contaminated surfaces (Ward et al. 1991). Evidence has shown that rotavirus can be readily transmitted from environmental surfaces either directly from surface-to-finger or from surface-tomouth (Ward et al. 1991). Its survival on environmental surfaces and hands has also been demonstrated (Sattar 1986; Ansari et al. 1988; Ward et al. 1991). In a study of two infant day care centres, Butz et al. (1993) showed that moist surfaces such as telephones, water fountains and water play tables were common sources of rotavirus contamination. Ward et al. (1991) demonstrated that 13 out of 14 adult subjects who consumed rotavirus (103 focus forming units) in a controlled laboratory experiment became infected. It was also found that rhinoviruses can survive for several hours on the hands, and that self-inoculation by rubbing of the nasal mucosa or conjunctivae with virus-contaminated hands can lead to infection in susceptible hosts (Hendley et al. 1973). The possibility that infection can result from direct contact with contaminated surfaces is supported by evidence showing that ingestion or contact with relatively small numbers of pathogenic organisms can be sufficient to cause infection. Investigations with healthy adults indicate that the infective dose of species such as Salmonella and E. coli may be as high as 106 to 107 colony forming units (cfu) but may be as low as 102 to 103 or even less depending on the strain involved (McCullough and Eisele 1951; Ferguson and June 1952; Lipson 1976; Hockin et al. 1989; Craven et al. 1975; Gill et al. 1983; Greenwood and Hooper 1983; D’Aoust 1985). Infective doses for Campylobacter and E. coli 0157 are estimated at 100-300 and 500 cfu (Tauxe 1992; Anon 1994b). For Staph. aureus it was shown that although an inoculum of up to 106 cfu may be required to produce pus in healthy skin, as little as 102 may be sufficient where the skin is occluded or traumatised (Marples 1976). 3. Home environment factors Although not appropriate for inclusion in guidelines on home hygiene, consideration also needs to be taken of social and environmental factors in the spread of infection in the domestic environment. Home design may influence hygiene in the home, such as the ability to clean toilet areas and other surfaces which may become contaminated within the home. Advice does, however, need to be included on the control of mould and fungal growth in the home because of the reported link with respiratory health, particularly in relation to asthma (Flannigan et al. 1991; Martin et al. 1987). 4. Groups who may particularly benefit from hygiene guidelines and education All people are at some risk of food-borne illness, but it must be recognised that certain sub-groups within the population are more susceptible to food-borne and other pathogens, than healthy young and middle-aged adults. In a normal healthy population, people are exposed fairly regularly to Salmonella but very few people become infected carriers and shedders, and only a small proportion become seriously ill. However, some Salmonella strains may be particularly hazardous to the elderly population. Guidelines should therefore highlight those groups at increased risk such as infants, pregnant women, the elderly and the immunocompromised (Wolf 1995). Although the care at home of infectious family members such as HIV or MRSA carriers returning from hospital is a specific healthcare issue, the general practices and principles which may be regarded as home healthcare procedures also apply to some situations which are considered as everyday matters in the home. This includes the care of babies who may cause faecal contamination of the home, the care at home of elderly people or of a family member or child with a gastrointestinal infection. It is important that both the infected person and those who have to care for them in the home have a good knowledge of hygiene practices. Such people would particularly benefit from an understanding of the idea of relative risk, which takes into account the susceptibility of different subgroups to different pathogen. INFECTION PREVENTION AND IMPROVING HYGIENE IN THE HOME Having identified the hazards and relative risks in the home, it is then necessary to give advice on appropriate hygiene procedures for implementation in each situation. Guidelines must outline which home hygiene measures for each situation can most effectively be applied to reduce potential infection risk. This needs to emphasise common sense procedures and provide more detailed instructions where appropriate. Preparing guidelines to address these issues must also take into account the best method of communicating the educational information to the public for maximum effect in order to positively influence behaviour. Advice on appropriate decontamination processes in the home Generally, there are a number of decontamination practices which can be encouraged in the home to ensure that food is wholesome to eat, and that sites and surfaces which represent a potential for cross contamination are hygienically clean and not just visibly clean. These include drying, detergent and hot water washing, heat and disinfection. Drying of contaminated items and surfaces plays a vital role in maintaining low levels of contamination. However there is evidence to suggest that many bacterial and viral species can survive for considerable periods of time even on dry surfaces and, for this reason, drying should not be considered as an effective means of achieving a hygienically clean surface, but only as a means of maintaining surfaces in a hygienic state. Studies have shown survival up to 4 hours for Gramnegative species like Salmonella and E. coli, and up to 24 hours at least for Staph. aureus (Scott and Bloomfield 1990). In many situations, such as the decontamination of cooking and eating utensils, detergent and hot water washing is adequate for achieving a hygienically clean surface. However, it must be emphasised that because the micro-organisms are removed by mechanical removal, detergent and water washing is only effective if applied with a suitable rinsing process. Since the purpose of the detergent is to facilitate detachment of the bacteria from the surface, cleaning products should therefore be formulated to maximise this effect. Heat is an effective form of disinfection although it may not be applicable to large surface areas and may be unreliable in unskilled hands. An early survey by Anderson and Gatherer (1970) showed that, although disinfection of infant feeding utensils can be consistently achieved under controlled laboratory conditions using either hypochlorite or boiling, disinfection failures were encountered more frequently with bottled and teats treated by mothers in the home using boiling (54 and 66%) as compared with hypochlorite (22 and 30%). Set against this however, heat is the method used to reduce contamination levels in foods to a level which is safe for consumption. The operating temperature of dishwashers is also generally sufficient for disinfection of contaminated cooking and eating utensils. Chemical disinfectants or hygienic cleaners are used for decontamination of sites and surfaces in situations where the former methods are either impractical or deemed to be inadequate for the particular situation. Chemical disinfection may also be particularly beneficial in high risk situations, for example where there are elderly persons, neonates or young pets in the home and where either the infection risk is increased or the consequences of infection are more significant. Since chemical disinfectants vary considerably in their properties, it is important that guidelines give information on the choice of a suitable disinfectant or hygienic cleaning product It is important to stress that the effectiveness of any hygiene procedure applied in the home depends not only on the effectiveness of the procedure (e.g. the hygienic cleaner or disinfectant) but also on the way in which it is applied i.e. in the right way and at the right time. Although the evidence shows that decontamination procedures will reduce the number of viable organisms to a safe level, the effects may be relatively short lived and recontamination of these sites may occur quite rapidly either as a result of recontamination or, for surfaces which remain damp, by the re-growth of residual survivors not destroyed or removed by the hygienic decontamination process. This clearly indicates that to achieve benefit, hygiene procedures should be applied for a specific purpose, rather than as part of a routine cleaning process. In using chemical disinfectants in the home there are a number of issues which suggest that inappropriate use or overuse of chemical disinfectants should be avoided. These relate to the development of resistant microbial strains, a lowering of natural immunity or environmental factors. SUMMARY AND CONCLUSIONS Epidemiological and microbiological data presented in this paper suggest an a priori need for an improvement in hygiene awareness and hygiene practices in the home. It was agreed that, as a first step to achieving this, “Home Hygiene Guidelines” , which draw together all aspects of home hygiene and healthcare related to infectious disease control, and give comprehensive and consistent information on procedures to prevent infection and the transfer of infection in the home, should be prepared. It was considered that such guidelines should be written with the specific intention of educating those hygiene professionals from whom the public receive information and guidance of home hygiene (i.e. those people whose job or profession involves advising the public on hygiene and healthcare). It was agreed that the most cost-effective approach (in terms of time and effort) to achieving improvements in home hygiene is to identify situations which represent the greatest risk and to ensure that hygiene advice and hygiene practice focuses on the reduction of the risks in these situations; a strategy which might aim to reduce the overall levels of microbial contamination in the home must be regarded as neither practicable nor desirable. Since the complexity of the various aspects of home demands that a “flexible approach” is adopted as appropriate to each specific situation or problem, it is recognised that the guidelines should aim to educate the user on the basic principles which underlie all aspects of home hygiene as well as provide practical advice on appropriate intervention measures for sites and surfaces etc. where a need for intervention is considered desirable. As with any educational programme, both hygiene professionals and members of the public are unlikely to achieve improvements in home hygiene unless they understand which practices in the home are most likely to contribute to the infection risk. An additional benefit of a total approach to home hygiene is that it encourages an understanding of the relative risks for different aspects of home hygiene; hitherto each of the components of home hygiene have tended to be considered only in isolation e.g. food hygiene and home healthcare. As stated by Scott (1996) improved awareness of good home hygiene practice and its importance would also have the benefit of developing a public better able to apply hygiene principles and practice in the community in areas such as day-care centres, residential homes, schools, restaurants and retail outlets. Whatever profession we choose to follow, our basic understanding of hygiene is developed in the home. 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