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Infection and immunity
Infection and immunity

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1.3  Acute or chronic conditions

Two useful terms that are equally relevant to infectious and non-communicable diseases (NCDs) refer to the time course of the illness. Knowing how long the symptoms of a disease have persisted and how quickly they are worsening or improving can help in making a diagnosis.

An acute condition is characterised by symptoms that develop rapidly and reach their peak within a few days or weeks. The patient either recovers relatively quickly or dies! Note that acute means ‘fast’ and ‘short-term’ – it does not necessarily mean ‘serious’. Some acute infections are mild and resolve in a short time without any treatment.

  • Can you identify an acute infectious disease that you or someone you know has suffered from in the past year, resulting in complete recovery within a week or two?

  • You may have suggested the common cold, or perhaps a stomach upset with an episode of diarrhoea. There are other possible examples.

By contrast, a chronic condition develops slowly and may take many months or years to reach its most severe extent. The term ‘chronic’ comes from Cronos, the Greek god of time. People with a chronic condition may cope well with its effects, but they may not fully recover the health they previously enjoyed. If left untreated, chronic diseases usually progress (get worse) and some conditions may result in permanent disability or loss of life. Tuberculosis (TB) is an example of a chronic infectious disease caused by bacteria that most often affect the lungs, but can also invade other parts of the body. TB progresses slowly but inevitably unless specific drugs are taken consistently every day for three-to-six months (Figure 3).

Figure 3  Tuberculosis requires consistent long-term drug treatment.

Most NCDs are chronic conditions, but some can have an acute episode – for example, people with cardiovascular disease (a chronic disease of the heart or blood vessels) can have a heart attack (an acute event).