Infectious diseases are the commonest afflictions of humans and are a major source of morbidity and mortality in both developed and developing countries. Table 1.1 shows estimated morbidity and mortality figures for the common infectious diseases. Increase in world travel in the past 30-40 years has brought Westerners into contact with a number of diseases unusual in the West, such as malaria and schistosomiasis.
New infective agents continue to be identified including Helicobacter pylori, the new hepatitis viruses C and E, the agent of Whipple’s disease, Tropheryma whippeii, and new diarrhoea-producing enteropathogens such as Cyclospora cayatenensis. Human immunodeficiency virus (HIV) infection continues to increase. There is an increasing problem of infections in the immunosuppressed, not only in those with HIV but also in organ transplant recipients and those receiving anticancer chemotherapy.
The control of infectious diseases worldwide has been vastly improved by the use of effective vaccines and antimicrobial agents. Technological advances in molecular
biology have also improved diagnosis, treatment and the development of new vaccines.