World health report

Press release

Why diseases are spreading

WHO says that thanks to concerted international action, some diseases are close to being eliminated or eradicated completely, among them poliomyelitis, leprosy, neonatal tetanus, guinea-worm infection and Chagas disease. Other targeted diseases such as onchocerciasis (river blindness) will soon follow. Extra resources must be mobilized to ensure that the campaigns against all of them continue - otherwise, progress already made will be compromised.

About 8 out of 10 of all the world's children have been immunized against six diseases - diphtheria, measles, neonatal tetanus, pertussis (whooping cough), poliomyelitis and tuberculosis.

But the outlook for many others is that they will continue to spread and become increasingly difficult to control, for a combination of reasons. These factors include:

  • Population growth combined with rapid urbanization means that many millions of city dwellers live in overcrowded and unhygienic conditions that are breeding grounds for infectious diseases.
  • Wars, civil turmoil and natural disasters mean that millions of migrants or refugees are on the move in conditions that are also fertile for infectious diseases.
  • Rapid increases in international air travel and the growing traffic in trade, particularly food trade, mean that disease-producing organisms can be transported within hours from one continent to another.
  • Expanding areas of human habitation place additional millions of people at risk from pathogens previously rare or unknown as causes of human disease.
  • Social changes including the clustering of young children in day-care centres and growing numbers of the elderly in nursing homes place these age groups at higher risk of infections.
  • Diseases formerly under control are re-emerging because of complacency towards them in the public health sector - tuberculosis is one example - and a revival of others, such as diphtheria, has been triggered by the collapse of public health systems because of economic or social crises.