The case is made that the high prevalence of common long-term conditions justifies describing them as modern plagues. The symptoms of the principal conditions are described. These conditions are considered in the context of their impact on curtailing healthspan - the age at which people cometo the end of their fully healthy lives. While medical healthcare has extended lifespan, the curtailment of healthspan results in years or decades of disability. This gap between healthspan and lifespan diminishes as deprivation declines.

While some risks for disease like our genetic make-up cannot be modified, many risks are amenable to reduction. The major modifiable risk factors for the modern plagues are outlined: our body mass index and obesity; our levels of physical activity; and degrees of social isolation. While infections spread through a population owing to the transmission of a physical disease agent, research shows that modifiable risk factors like obesity spread via social networks. These modifiable risk factors all arise from modern ways of life. This term is preferred to ‘lifestyle’ which implies that way of life is a matter of individual choice. This chapter looks at the definition of obesity, its prevalence and its transmission through social networks. It considers historical change in the prevalence of physical activity and recommendations on optimal levels of such activity, the rise of social isolation, and the risks that arise from the current modern way of life.

Diagnosis of one of the modern plagues is simply the beginning of the accumulation of disabilities at the end of healthspan. Other long-term conditions – including more than one modern plague - tend to arise after the diagnosis of the first one. Individuals must endure successively increasing numbers of long-term conditions. Diabetes is associated with increased risk of heart disease and damage to nerves, kidneys, eyes and feet. Conversely, smoking, alcohol and pollution are among the risk factors for the modern plagues.

Implementing Systems Prevention requires a re-examination of the meaning of ‘health’. A positive definition is needed to replace the negative definition (absence of disease) that is common currency. Political philosophy provides this positive definition. Lawrence Hamilton is concerned with the role of values versus the role of needs in democratic discourse. He recognises that human needs change and he describes some basic categories of these needs. He equates ‘health’ with satisfaction of these needs. In this chapter, these needs are discussed using insights from biology and ‘health’ is redefined as the optimal satisfaction of these needs. The needs are contrasted with definitions of health by the World Health Organisation.

Epidemiology aims to understand, prevent and control diseases and conditions that affect populations of plants, animals or humans. Its method rests on observation and action. When applied to a health problem it leads to conclusions on prevention. The father of epidemiology, John Snow, used his observations to advocate actions by government that he predicted would curtail a major cholera outbreak in Victorian London. However, this experimental approach was soon abandoned so that, today, epidemiology has become primarily an observational science. The case is made for the rebirth of epidemiology combining observation and experiment.

The Covid-19 pandemic provides contemporary evidence on the parallels between ending an infectious pandemic and ending pandemics in the modern plagues.

By considering health as the status of an individual when their needs are optimally satisfied, it becomes apparent that health cannot be the responsibility of a specialised arm of government. It needs to be the driver of public policy as a whole. This general principle finds its roots in Cicero and has been endorsed by political philosophers of the Enlightenment. The limited successes are discussed of an untheorized Systems Prevention in some modern institutions (Public Health England, the Health and safety Executive and the NHS Health Check). Research projects that might be the basis for Systems Prevention are described. The authors describe their own research experience that underpins the plea of this book to deliver Systems Prevention consciously. This experience includes work on developing the infrastructure required for health improvement.

This chapter summarises the book’s messages and proposals for change. The Health Society relies on a consensus that ‘your health is my health’. Achieving that consensus requires the countering of objections. These are considered and their weaknesses exposed. Synergy is noted between health as needs-satisfaction and action against global heating.