‘Epidemics and pandemics’ considers cyclical endemics of viruses, vaccination programmes, and the spread of viruses from one continent to another — pandemics. Airborne viruses mainly cause respiratory illnesses, like flu, the common cold, or pneumonia, and those transmitted by faecal–oral contamination, like rotaviruses and noroviruses, cause intestinal upsets with nausea, vomiting, and diarrhoea. These are described in detail. Many virus families that rely on faecal–oral transmission produce similar symptoms in animals, resulting in great economic loss to the farming industry. Rinderpest virus, the cause of cattle plague, is closely related to the measles virus. The growing problem of hospital-acquired infections is also discussed.