As stated previously, it must be borne in mind that cross infection in the domestic environment does not always result in an infectious disease. The risk of infectious disease arising from transfer of microorganisms in the domestic environment depends on a number of factors including the type of organism and its pathogenicity, the infective dose, the susceptibility of the host (neonates, geriatrics, pregnant women and other immunocompromised people are at increased risk of infection) and the route by which the organism enters the body.

It is not possible to quantify the risks of infection for a particular organism in relation to a particular host. Figure 1 gives an illustration of the way in which the infection risk increases according to the nature of the infecting microorganism and the susceptibility of the host. From this, certain high risk situations and groups can be identified where the application of additional and/or more rigorous hygiene measures over and above those which are routinely employed is recommended. Such measures are also required in situations where infected family members represent a source of infection to others.

Figure 1. A simplified illustration showing the increasing risk of infection according to the pathogenicity of the infecting microorganism and the immune status of an individual

4.1.1. Neonates
Neonates and young babies (0-1 years old) are at increased risk of infection. In addition, procedures such as nappy changing carry an increased risk of transmission of gastrointestinal infection through faecal contamination of hands and hand contact surfaces, and most particularly of face cloths and sponges where organisms can grow at ambient temperatures to establish permanent reservoirs of contamination. Disposal of nappies also poses an increased risk of faecal contamination of reservoir sites such as the toilet water, toilet bowl and toilet seat.

In addition to normal hygiene routines the following situations therefore require rigorous hygiene procedures: hygiene of infant feeding utensils, personal hygiene to prevent infection and self infection (particularly eye infection), nappy hygiene and the hygiene of toilet training equipment (potties).

Hygiene of feeding utensils:

• Feeding utensils should be decontaminated by boiling or by use of a suitable disinfectant product. Note: these products are often referred to commercially as "sterilising products" whereas in practice they achieve disinfection

Nappy changing:

• Used disposable nappies should be sealed in a plastic receptacle and placed in the waste.
• Reusable nappies should be placed in a nappy bucket and disinfected using a disinfectant product. After disinfection the contents of the nappy bucket should be flushed down the toilet - NOT poured down the kitchen sink.
• Vessels used for washing and cleaning nappies may also become heavily contaminated. In these situations, additional measures need to be considered.
• After disinfection soiled reusable nappies together with any other soiled clothing should be laundered (see Section 1.3).
• All objects and surfaces which were touched and may have become contaminated with faecal material during and after nappy changing should be cleaned and disinfected

4.1.2. Geriatrics
There are increasing numbers of elderly people who will be living at home, either alone or as part of a family group, who may be at increased risk of infection, including foodborne infection, due to the effects of ageing on their immune system. A proportion of elderly people may also be bedridden or incontinent, requiring particular attention towards laundry hygiene.

4.1.3. Pregnant women
Pregnant women in the home are at increased risk from infections, such as Listeria, rubella, varicella, and should be given appropriate advice on the prevention of acquiring these infections in the home environment. Although primarily recognised as a foodborne pathogen, Listeria species are common in the domestic setting and may be found outside the kitchen, particularly in wet areas (Beumer 1996). Advice on the prevention of Listeria-associated foodborne illness is provided by the Centers for Disease Control in the United States (Anon 1992b). Toxoplasmosis represents a significant problem in pregnant women, who should take precautions to avoid contact with, or cross-infection, from cats that sometimes harbour this pathogen.

4.1.4. Immunocompromised people/patients discharged from hospital
Immune compromised patients discharged from hospital into the home are at increased risk from all types of infection and should be given appropriate advice on the prevention of acquiring these infections in the home environment.

• Persons infected with HIV living at home should receive advice on the prevention of opportunistic infections. Advice to HIV patients about the avoidance of exposure to opportunistic pathogens has been published (Anon 1995a).
• Patients and caregivers need to take special precautions regarding the monitoring, insertion, use and maintenance of intravenous catheters in the home healthcare setting. Guidelines for i.v. care have been published and patients or caregivers can be taught to maintain the i.v. system according to these guidelines (Simmons et al. 1982; Simmons et al. 1990)

4.1.5. Contact lens wearers
The eye is at great risk from contamination by contact lenses and these should be disinfected using a recognised preparation. The method for employing these preparations should be carried out rigorously according to the manufacturer's instructions.

4.2. The infected family member as a source of infection

4.2.1. Symptomless carriers of infectious disease
There are a number of categories of people who may be present in the home and who represent a source of serious, and in some cases life-threatening, infection in the home. These include, for example, symptomless carriers of primary pathogens, such as Salmonella, Campylobacter, rotavirus, Cryptosporidium, carriers of MRSA and carriers of hepatitis.

In many cases it is not possible to identify these people as carriers, but where they are identified hygiene precautions as outlined in these guidelines should be rigorously implemented. It is important that the families of infected people are educated about how the diseases are transmitted so that appropriate precautions are taken but also to promote ordinary family interactions by alleviating concerns about transmission.

For carriers of bloodborne diseases such as HIV and hepatitis B and C universal blood and body fluid precautions should be implemented in the home healthcare environment (Anon 1987; Anon 1988).

Generally, the following procedures are recommended:

• Whenever contact with blood or body fluids is anticipated, safe practices and appropriate barrier precautions should be used to prevent percutaneous, mucous membrane and skin exposures to bloodborne pathogens.
• Gloves should be used for touching blood, body fluids, mucous membranes or areas of broken skin and for handling items soiled with blood or body fluids.
• Hands should be washed after removing gloves which have come into contact with these sources.
• Blood and blood-containing fluids spilled on surfaces should be promptly removed and the contaminated surfaces cleaned with a disinfectant product (Simmonds and Chanock 1993).
• Gloves should be used during cleaning and decontaminating procedures.
• Carriers of bloodborne infections should not share razors, toothbrushes or any other object which may become contaminated with blood

For carriers of MRSA, guidelines on its control have been published and include the following recommended procedures (Anon 1995b):

• Handwashing is one of the most important practices in preventing the spread of MRSA and MRSA carriers should be encouraged to practice good hygiene.
• The carrier as well as other family members should adhere to good infection control procedures.
• In certain cases, hand disinfection using an alcohol solution may be necessary

For carriers of pathogens which are primarily transmitted through the faecal-oral route, such as hepatitis A or enteric pathogens such as Salmonella, Shigella, Campylobacter and rotavirus, particular attention to personal hygiene and handwashing will minimise the risk of transmission.

4.2.2. Family members suffering infectious outbreaks
In addition to symptomless carriers of infectious diseases, family members suffering infectious outbreaks such as diarrhoea, acute hepatitis A, skin or eye infections, must follow more rigorous personal hygiene procedures to minimise the risk of transmission.

4.3. Treatment of minor injuries
Animal bites, insect bites and stings, abrasions, cuts, burns and scalds may be responsible for a range of injuries in the home which may become susceptible to infection or a source of cross infection to others.

• A first aid kit should be kept fully stocked in all homes for the treatment of minor injuries. This must be kept out of the reach of any children.
• The application of antiseptics may, in the case of a dirty wound, contribute to prevention of infection. There is however a body of opinion which suggests that the use of antiseptics can delay healing of healthy tissues, and this practice is therefore no longer encouraged for minor "clean" injuries

First aid measures for a range of conditions or injuries are listed in a handbook for child care providers published by the Centers for Disease Control and may be equally applied for injuries occurring in the home (Hale and Polder 1996).