gms | German Medical Science

For a time during the 20^th Century, ready access to water and sanitation, combined with the availability of vaccines and antibiotics, seemed to offer the possibility that infectious disease (ID) would someday become a thing of the past. As a result hygiene has received declining attention in recent decades. Nowhere is complacency about hygiene more evident than in the home. Now at the turn of the century, ID is moving back up the health agenda. Current concerns focus on foodborne, waterborne, and other infectious intestinal diseases, which remain at unacceptably high levels, on antibiotic resistance which compromises treatment of bacterial diseases, on viral agents which are not treatable by antibiotics, and on new agents (e.g SARS, flu) and their potential for rapid global spread. Pathogens are also now increasingly implicated as co-factors in cancers and some degenerative diseases. In the developing world there is consensus that, one of the past mistakes, has been to give priority to water over sanitation and to sanitation over hygiene. In reality it is hygiene (e.g. keeping faecal matter away from hands, food and water, preventing cross contamination etc.) that reduces the burden of ID. Of particular concern, both in developed and developing countries is the rising proportion of the population who are more vulnerable to infection. This includes the elderly, the very young, people with chronic or degenerative illness; and immuno-compromised patients discharged from hospital. Currently, about 1 in 6 persons in the UK belongs to an ‘at risk’ group, and it is likely that the same applies in most European countries. All of these groups, together with family members who carry HIV/AIDS, are increasingly cared for at home. If ID is to be contained in a manner that is economically sustainable, responsibility for hygiene must be shared by the public, who in turn must be properly and responsibly informed. Complacency about home hygiene has led to a lack of understanding of the basic difference between “dirt” and “germs”, between “cleanliness” and “hygiene”, and between “cleaning” and “disinfection”. The confusion has fostered the idea that hygiene means creating a “germ-free” home.

Although there is awareness amongst public health scientists about the importance of renewed emphasis on hygiene, this does not necessarily translate into commitment to action by national and international government and non-government agencies. A significant barrier to progress is the fact that, in most countries, the separate aspects of hygiene (household water, safe faeces disposal, food hygiene, handwashing, care of “at risk” groups, etc.) are dealt with by separate agencies, with the result that hygiene promotion tends to be fragmented and ineffective. Growing interest about home hygiene has led an international group of experts to form the International Scientific Forum on Home Hygiene (IFH; http://www.ifh-homehygiene.org/). A key feature of IFH is that it looks at hygiene holistically from the point of view of the family and the range of problems they face in order to reduced ID risks.

In the past few years, research studies focussing on the home have given us a better understanding of how ID is spread in this environment, and how the risks can be reduced. Using this data, IFH has developed an approach to home hygiene based on the concept of risk assessment and risk prevention. This approach is now well accepted as the most cost effective means of infection control in hospitals, food manufacturing, and other settings. “Targeted hygiene”, as it has come to be known, starts from an acceptance that homes always contain harmful microbes (from people, pets, food, etc.) and that good hygiene is not about eradicating them through day to day cleaning, but about targeting measures in the places and at the times that matter, in order to limit risks of exposure. Since targeted hygiene focuses on preventing spread of germs, major target sites in the home are the hands and hand and food contact surfaces in the kitchen, bathroom and toilet. Cleaning cloths are also critical factors. Intervention at the appropriate time (i.e during raw food handling, rather than as part of daily routine) is an equally fundamental part of targeted hygiene.

Access to safe and effective hygiene procedures for reducing these risks is also a part of targeted hygiene. Since evidence now shows that the “infectious dose” for many common pathogens such as Campylobacter, norovirus and rhinovirus can be very small (1-500 particles or cells) intuitively one must argue that, in situations where there is significant risk (e.g. during food preparation), the aim should be to get rid of as many germs as possible from sites and surfaces involved. In general, for cooking and eating utensils and the hands, the evidence suggests microbial contamination can be effectively removed using soap or detergent and hot water. However, since this process relies on mechanical removal of microbes, to be effective it must be applied in conjunction with a rinsing process. A range of studies now show that, although cleaning surfaces with a cloth or mop removes a large proportion of the bacteria or viruses present, it also spreads residual cells or particles in significant numbers around the surface and onto the cloth to be spread to other surfaces. This suggests that, in situations where thorough rinsing is not an option, and where failure to achieve hygiene carries serious risks (e.g. food hygiene), use of a disinfectant product or a heat process which kills germs is advisable.

In devising hygiene policy it must be borne in mind that the home is fundamentally different from hospitals and other settings. The availability of data focussing on the home now allows us to do this. Although infection risks may be less than in hospitals, the level of understanding of hygiene may be poor. Facilities for maintaining hygiene e.g kitchen facilities may be inadequate, overcrowding may be a problem, and domestic animals are an added risk. In addition there may be family members who are more vulnerable to infection, or who pose an infection risk to others. For these reasons also, it may be advisable, for certain situations, to recommend hygiene procedures which carry a higher margin of safety such as those involving a disinfectant product.

In formulating home hygiene policy we must also be mindful of concerns about antimicrobial resistance, and the possible impacts of cleaning agents and disinfectants on the environment. A further issue is the hypothesis which proposes that, a major cause of the rising incidence of allergic disorders that has occurred over the last 30 years, is declining microbial exposure. Because it is called the hygiene hypothesis, the popular notion has arisen that it is because we are “being too clean”. This is despite the fact that there is no good evidence to support this latter suggestion, or the hypothesis that overuse of disinfectants may contribute to development of antibiotic resistance in clinical practice. All of these issues have the potential to seriously undermine our attitudes to hygiene. Although they cannot be fully resolved in view of our incomplete picture of the scientific facts, perhaps it is time that we stop focusing on them as separate issues, and look at them in the context of the importance of ID and the need for effective prevention. Whatever the reality about the hygiene hypothesis, antimicrobial resistance and so on, the “targeted hygiene” approach as described above offers a way forward, because it seeks to maximise protection against ID, whilst disturbing the normal balance of our human and natural environment to the least extent. The data suggests that, when used as part of a targeted approach to hygiene, disinfectants have a role to play in preventing infection transmission in the home.

Figure 1 [Fig. 1]

Consultant in Infectious Disease and Hygiene, Chairman and Member of the Scientific Advisory Board of International Scientific Forum on Home Hygiene, Honorary Professor at the London School of Hygiene and Tropical Medicine.

Professor Bloomfield was awarded the Rudolf Schuelke Hygiene Prize in 1995, for her outstanding contribution in the field of Hygiene and Preventive Medicine.

She has been a member of several UK and international bodies including Comité Européen de Normalisation – CEN TC 216 – Antiseptics and Disinfectants.

Professor Bloomfield has published widely with over 100 publications in peer review journals and contributions to edited works.