Infectious diseases still kill more people than car accidents, cancer or war - 17.3 million in 1995 alone, and the numbers are increasing. Many of the factors in this rising incidence are environmental: from deforestation to contaminated water, global warming, the shift of populations from rural locations to cities and mobility from globalization.
Infectious diseases remain great killers in the developing world, the six most serious taking the lives of millions every year; and parasitic diseases remain rampant. More parasites, bacteria and vectors are becoming resistant to more drugs and pesticides, creating additional problems for the control of several diseases. While the average life expectancy at birth improved steadily almost everywhere during the 1970s, in many of the least developed countries it is still less than 50 years.
The greatest challenges for environmental medicine in the years to come lie in the less developed regions, especially in curbing parasitic infections and the diseases of squalid settlements, rather than in the developed countries, where the indications are that environmental factors are not major causes of premature mortality and where a major challenge to medicine is to overcome the so-called diseases of civilization (such as coronary heart diseases, cancer, hypertension, etc) and social and behavioural problems, and to adopt the pattern of health care more closely to the needs of people.