Spread and prevention of some common viral infections in community facilities and domestic homes.

Abstract

Nearly one thousand different types of viruses are known to infect humans and it is estimated that they account for approximately 60% of all human infections (Horsfall 1965). Viruses are spread easily through closed environments such as the home, schools, workplaces, transport systems, etc. Although many of the respiratory and gastrointestinal infections caused by viruses can be asymptomatic or relatively mild and self‐limiting (coughs and colds, etc.), they still represent a significant economic burden. Increasing numbers of people who have reduced immunity to infection, for whom the consequences of infection can be much more serious, are now cared for at home. At risk groups include not only the immunocompromised but also the elderly, neonates, pregnant women, hospital patients discharged into the community, individuals using immunosuppressive drugs and also those using invasive systems (indwelling catheters) or inhalation systems or devices. Otherwise healthy family members with asthma or allergies also have increased susceptibility to infection. In the UK it is estimated that one in six people in the community belong to an ‘at risk’ group (Bloomfield 2001). World Health Organisation estimates suggest that, by 2025, there will be more than 800 million people over 65 years old in the world, two‐thirds of them in developing countries (Anon. 1998). Viruses are probably the most common cause of infectious disease acquired within indoor environments. Close personal contact within the home and community settings, such as daycare centres and schools, makes them ideal places for the spread of viral infections. Infected individuals can shed up to 1012 virus particles per ml of faeces with the possibility of transfer of the virus by contaminated hands to surfaces in the bathroom or toilet. Viruses that cause tonsillitis, colds, croup, bronchiolitis, influenza, pneumonia and other respiratory tract infections can be spread in aerosolized droplets. Aerosols produced by coughing, sneezing and talking can be inhaled directly by a susceptible host or may settle onto surfaces. Touching hands or fomites, such as eating utensils, towels or doorknobs, inadvertently contaminated with fresh secretions or vomit, etc. from an infected person and then transferring the virus from the hands to the eyes, nose or mouth, are further routes of spread. Infants are especially vulnerable to such infections because they frequently place objects, such as toys, into their mouths. Transfer of viruses to food during handling and preparation via hands and food contact surfaces is an important route of spread of viral gastroenteritis. Amongst health care professionals there is growing awareness that improved standards of hand, surface and air hygiene in community settings could do much to prevent the spread of viral infections within these environments. The purpose of this paper is to review the evidence base for this assumption. Since viral infections are not easily treated, prevention of infection is still the main route of control. Assessment of the impact of hygiene is made difficult by the general lack of quantitative epidemiological data and, even where evidence for cross‐contamination as a causative factor in an outbreak exists, it is always circumstantial. A further problem in assessing whether contamination found on hands or other surfaces might represent a hazard is that the infectious dose can vary significantly according to the pathogenicity of the organism and the immune status of the host. Thus the case for practising good hygiene in these settings rests largely on evidence showing that cross‐contamination can occur in these environments coupled with laboratory data demonstrating the efficacy of hygiene procedures in minimizing microbiological contamination.