Disease prevention is a central pillar of public health practice. Classically, disease prevention is a biomedical approach aimed at addressing the burden of ill health. Within the biomedical framework disease prevention has three phases: primary, secondary and tertiary. Prevention may be accomplished in the pre-disease state by measures designed to promote general optimum health or by the specific protection of human beings against disease agents or the establishment of barriers against agents in the environment. These procedures have been termed primary prevention. As soon as the disease is detectable, early in pathogenesis, secondary prevention may be accomplished by early diagnosis and prompt and adequate treatment. When the process of patho-genesis has progressed and the disease has advanced beyond its early stages, secondary prevention may also be accomplished by means of adequate treatment to prevent and limit disability. Later, when defect and disability have been fixed, tertiary prevention may be accomplished by rehabilitation (Leavell and Clarke, 1965: 20). KEY POINTS •
Influence of the biomedical model on disease prevention.

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Primary, secondary and tertiary approaches to disease prevention.

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Application of the epidemiological triangle in the management of disease processes and prevention.

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Role of health promotion, education and individual health behaviours.

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Influence of policy drivers on disease prevention strategies.

DISCUSSION Prevention, although utilised since early antiquity, significantly developed during the epidemiological revolution of the nineteenth century. At this time reduction in morbidity and mortality was achieved through social and environmental reforms in hygiene, housing, sanitation and working conditions (Rogers, 2003). Changes in morbidity and mortality shifted the focus of health policies away from disease to health behaviours and led to the rise in health education. This aimed to inform individuals about the outcomes of risky health behaviours. In the latter part of the twentieth century a reawakening of the effectiveness of disease prevention occurred within public health. The rationale for this development lies in an understanding of the 'prevention paradox'. According to Baggott (2000) preventative measures which benefit the population have little appeal to each individual. This means that left to their own devices, individuals have little incentive to contribute to activities that improve their health. Therefore, measures aimed at the individual should be replaced or enhanced by greater influence from the state to address the public's health. To support this paradox is a greater understanding that the preventative model, which focuses on individualism and which takes little account of the determinants of health, can cause an increase in health inequalities. Those in privileged positions will attain better health than those dependent on the state for health interventions (Tones and Green, 2004). Individualism has been superseded by socialist ideologies as the dominant approach to addressing ill health. This ideological shift means that greater emphasis is now placed on disease prevention through legislative action and via the reorganisation of health services to address health issues. Depending on one's ideological viewpoint prevention can be viewed as an egalitarian act or as an oppressive mechanism of social control. The basic premise for undertaking disease prevention can be understood by an awareness of the epidemiological triangle (see Figure 29.1). An agent may be thought of as a substance that must be present for a disease or condition to occur. Transmission of an agent to a host may be accomplished in a variety of ways: infectious agents such as bacteria, viruses and parasites by contact; chemical agents such as toxic chemicals or pesticides may be inhaled, or absorbed through the skin; poisons may be ingested.