The struggle for control
Infectious diseases range from those occurring in tropical areas (such as malaria and dengue haemorrhagic fever) to diseases found worldwide (such as hepatitis and sexually transmitted diseases, including HIV/AIDS). Transmission can occur by direct person-to-person contact, through insects and other vectors, by way of contaminated vehicles such as water or food, and in other more complex ways. Today there are ominous trends on all fronts.
A few examples illustrate the impact of infectious diseases on human health and development:
- malaria - the worst of the vector-borne diseases - still strikes up to 500 million people a year, killing at least two million;
- acute lower respiratory infections kill almost four million children every year. Tuberculosis, similarly spread from person to person, kills three million people annually;
- diarrhoeal diseases, mainly spread by contaminated water or food, kill nearly three million young children every year;
- the AIDS virus, predominantly transmitted sexually, has already infected up to 24 million adults, of whom at least four million have died. More than 330 million cases of other sexually transmitted diseases occurred in 1995;
- viral hepatitis is rapidly emerging as a global health issue. At least 350 million people are chronic carriers of the hepatitis B virus and another 100 million are chronic carriers of the hepatitis C virus. Up to a quarter of them will die of related liver disease. The hepatitis E virus is a major cause of acute hepatitis;
- some cancers are caused by viruses (hepatitis B and C among them), bacteria and parasites. WHO estimates that 15% of all new cancer cases could be avoided by preventing the infectious diseases associated with them. Cancer as a whole is the second most common cause of death in many parts of the world. Ten million new cases were diagnosed in 1995.