These are illnesses which can result in death if they are not correctly managed. Every effort must be made to prevent them, recognise them early and treat them correctly. Many serious illnesses which are rarely seen in children in developed countries, are still major problems in poor communities with overcrowding.

Important serious illnesses include:

• Acute rheumatic fever
• Acute glomerulonephritis
• Septicaemia, especially meningococcal septicaemia
• Meningitis
• Pyelonephritis

Some serious illnesses, such as pneumonia and typhoid, are discussed in other units.