The goal of public health is to improve the overall health of a population by reducing the burden of disease and premature death. In order to monitor our progress towards eliminating existing problems and to identify the emergence of new problems, we need to be able to quantify the levels of ill health or disease in a population. Researchers and policy makers use many different measures to describe the health of populations. In this chapter we introduce more of the most commonly used measures so that you can use and interpret them correctly. We first discuss the three fundamental measures that underlie both the attack rate and most of the other health statistics that you will come across in health-related reports, the incidence rate, incidence proportion (also called risk or cumulative incidence) and prevalence, and then look at how they are calculated and used in practice. We finish by considering other, more elaborate measures that attempt to get closer to describing the overall health of a population. As you will see, this is not always as straightforward as it might seem.

A remedy is specific when the plaintiff seeks to get the court to coerce the defendant into doing (or not doing) a particular thing. The word ‘coercion’ is used advisedly. The court orders the defendant to do (or not to do) the particular thing, and if the defendant refuses to comply, the court may use measures such as imprisonment, sequestration and fines to encourage compliance with its order. The two most important examples of specific relief in Australia are the decree of specific performance and the injunction. This chapter will consider specific performance, and the next chapter will consider injunctions. Specific performance relates to ordering the defendant to comply with the terms of a contract, but injunctions may be ordered across private law and beyond. Specific performance is exclusively equitable, and generally operates in relation to a common law cause of action; namely, breach of contract.

Australian courts may grant ‘reasonable fee’ awards where defendants have used certain property or infringed certain rights in a tortious manner. ‘Reasonable fee’ refers to a method of calculating a monetary award for a wrong; namely, where the court awards the objectively ascertained fee that the parties would have agreed upon for permitting the defendant’s conduct. Reasonable fee awards may be made in various forms, including through an award of compensation, in an action for money had and received through ‘waiver of tort’, as ‘restitutionary damages’, or under Lord Cairns’ Act in lieu of an injunction. They are generally awarded for common law causes of action. As discussed in this chapter, the rationale for reasonable fee damages is highly contested. In previous editions of this book, we conceptualised reasonable fee awards as being gain-based and discussed them in the chapter on gain-based relief. The latest cases from the apex courts of the United Kingdom and Singapore suggest that reasonable fee awards are an instance of ‘substitutive compensation’. It remains to be seen whether Australian courts will adopt this approach.

Rescission is a form of relief which is available in respect of a variety of transactions (contract, gifts and conveyances) where one of the parties is subject to a vitiating factor (such as duress, fraud or misrepresentation) and she wants to get out of or ‘set aside’ the transaction. Rescission allows her to reverse the transaction. It has been said that ‘[t]he basic objective of the relief given upon rescission is to restore the parties to their original positions or, where rescission occurs in equity, as near to those positions as may be’. There is no requirement for the party seeking to rescind to suffer loss in the sense in which this is understood in the context of compensatory damages: she merely has to point to a vitiating factor. Although the party seeking to rescind can set aside the transaction, it is not voided: rather, it is rendered ‘voidable’. In other words, a voidable contract is valid and effective unless and until the plaintiff elects to rescind it. However, once a contract is rescinded it ‘is treated in law as never having come into existence’, although it is recognised that it formerly existed. All unperformed obligations under the contract are extinguished once a contract has been rescinded. The contract is extinguished as from the beginning (ab initio).

The concept of ‘remedy’ used in this chapter encompasses a court order replicating a preexisting right, not a response to civil wrongdoing. Restitutionary remedies responding to unjust enrichment differ from remedies responding to a wrong (breach of contract, tort, or equitable wrong). As noted in Ch 1, they do not fit easily into a division between the primary right and the secondary remedy. It is for this reason that the cause of action and the remedy overlap, and they are notoriously difficult to untangle. Discussions of restitutionary remedies inevitably turn into discussions of the cause of action.

This chapter deals with the availability of the other specific remedy: the injunction. As with specific performance, injunctions are a coercive remedy originating in equity. The court orders the defendant to do something (or to refrain from doing something) and the defendant must obey this order or be in contempt of court. Again, if the defendant does not comply, the court may use measures such as imprisonment, sequestration, and fines to encourage compliance with its order.

However, in contrast to specific performance, injunctions apply to many situations, not just contract or contract-like obligations, and they protect many private law rights, including rights in land, goods and other property, economic rights, the right to bodily integrity, the right to reputation, the right to privacy, and contractual rights. They may also be used in support of public law rights.

Epidemiology is about measuring disease or other aspects of health in populations, identifying the causes of ill-health and intervening to improve health, and we come back to these three fundamental components later in the chapter. But what do we mean by ‘health’? Back in 1948, the World Health Organization defined it as ‘… a state of complete physical, mental and social well-being’ (WHO, 1948). In practice, what we usually measure is physical health, and this focus is reflected in the content of most routine reports of health data and in many of the health measures that we will consider here; however, there are now methods to capture the more elusive components of mental and social well-being as well. Importantly, the WHO recognised that it is not longevity per se that we seek, but a long and healthy life. So, instead of simply measuring ‘life expectancy’, WHO introduced the concepts of ‘health-adjusted life expectancy’ (HALE) and subsequently ‘disability-adjusted life years’ (DALYs) to enable better international comparisons of the effectiveness of health systems.

Every civil wrong has a number of requirements that must be satisfied before the plaintiff may obtain compensation for resulting harm. One requirement common to all wrongs is that the harm must be attributable to the defendant’s wrongful conduct. It may broadly be said that the defendant’s wrongful conduct must constitute a cause of the harm. This always involves an inquiry into whether there is a historical link in fact between the wrong and the harm, and usually also a value judgement on whether liability for the harm ought to be imposed upon the defendant.

With regard to wrongs actionable only on proof of damage (for example, negligence), the attribution of responsibility for harm is part of establishing liability rather than a matter of remedy. With regard to wrongs actionable per se, the attribution of responsibility for harm is a matter of remedy since nominal damages can be awarded in the absence of loss. In any event, it is customary to discuss attribution of responsibility in books on remedies, and this book follows that custom.

People live complicated lives and, unlike laboratory scientists who can control all aspects of their experiments, epidemiologists have to work with that complexity. As a result, no epidemiological study can ever be perfect. Even an apparently straightforward survey of, say, alcohol consumption in a community, can be fraught with problems. Who should be included in the survey? How do you measure alcohol consumption reliably? All we can do when we conduct a study is aim to minimise error as far as possible, and then assess the practical effects of any unavoidable error. A critical aspect of epidemiology is, therefore, the ability to recognise potential sources of error and, more importantly, to assess the likely effects of any error, both in your own work and in the work of others. If we publish or use flawed or biased research we spread misinformation that could hinder decision-making, harm patients and adversely affect health policy. Future research may also be misdirected, delaying discoveries that can enhance public health.

Legislation in all Australian jurisdictions allows courts to award damages either in addition to, or in lieu of, specific performance or an injunction. Although damages awarded under this legislation are sometimes known as ‘equitable damages’, to avoid confusion with equitable compensation, they are called ‘Lord Cairns’ Act damages’ in this book.

Lord Cairns’ Act damages are primarily awarded for proprietary torts such as trespass, and for breaches of contract or negative covenant where no other relief is available (either because it is impossible or for discretionary reasons). Their calculation varies according to the facts of the individual case, and the rules are complex. They have also been awarded for equitable or statutory wrongs, but this is controversial.

As noted in this chapter, the placement of this remedy within a functional structure presents difficulties. Lord Cairns’ Act damages have been said to perform multiple functions including compensation and restitution. Strictly speaking, they do not compel performance, but award money instead. However, because they are a monetarised version of specific relief, they follow specific performance and injunctions for the pragmatic reason that they ‘fit’ best here.

The search for the causes of disease is an obvious central step in the pursuit of better health through disease prevention. In the previous chapters we looked at how we measure health (or disease) and how we look for associations between exposure and disease. Being able to identify a relation between a potential cause of disease and the disease itself is not enough, though. If our goal is to change practice or policy in order to improve health, then we need to go one step further and decide whether the relation is causal because, if it is not, intervening will have no effect. As in previous chapters, we discuss causation mainly in the context of an exposure causing disease but, as you will see when we come to assessing causation in practice, the concepts apply equally to a consideration of whether a potential preventive measure really does improve health.