"Fatal complacency" means that diseases once thought to be subdued - such as tuberculosis and malaria - are fighting back, and other infections are now so resistant to drugs they are virtually untreatable. Nearly 50,000 people a day are dying, often from diseases that could be prevented or cured for as little as a dollar per person.
At least 30 new infectious diseases have emerged in the last 20 years including HIV/Aids (which 26.6 million adults could be living with by 2000) and Ebola fever, which was fatal in 80 per cent of cases when it struck in Zaire in 1995. The WHO also notes that "fears are growing of a possible food-chain link between bovine spongiform encephalopathy and a form of the incurable Creutzfeldt-Jakob disease in humans".
Migration, global travel, and rapid population growth mean that disease- producing organisms are being transported from one continent to another. In March, the WHO and Unicef declared as an international health emergency the diphtheria epidemic sweeping the independent states of the former USSR. Europe now accounts for 80 per cent of the world's diphtheria cases.
The number of registered cholera cases in the WHO's European region also increased ninefold from 1993 to 1994. Tuberculosis strains resistant to drugs are increasing, and the number of cases of malaria, a nearly forgotten disease in 1980s Europe, has risen sharply.
In Britain, there have been 25 cases of diphtheria imported between 1990 and 1994, and nearly 40 cases of imported cholera from 1993 to 1995. Tuberculosis has remained constant at around 5,500 to 6,000 cases a year.
Until recently, antibiotics were regarded as the solution to many infectious diseases, but they are becoming less effective as resistance to them spreads. All bacteria possess an inherent flexibility to evolve genes that render them resistant to antibiotics. But because they have been used by too many people to treat the wrong kind of infection, that resistance has speeded up.
"The implications are awesome," says the report. "Drugs that cost tens of millions of dollars to produce and take perhaps 10 years to reach the market have only a limited lifespan in which they are effective. As resistance spreads, that lifespan shrinks; as fewer new drugs appear, the gulf widens between infection and control."
Successes for the WHO include poliomyelitis, cases of which have dropped 85 per cent since 1988, and eight out of ten children worldwide are now vaccinated against six major childhood diseases. But without concerted global action, the success in completely eradicating smallpox will not be repeated, the organisation warns.
"Despite the emergence of some 30 new diseases in the last 20 years, there is still a lack of national and international political will and resources to develop and support the systems necessary to detect them and stop their spread. Without doubt, diseases as yet unknown, but with the potential to be the Aids of tomorrow, lurk in the shadows."
Hirosh Nakajima, director-general of the WHO, identified a number of priority areas. He said extra resources must be mobilised to eliminate illnesses such as polio and guinea-worm disease; surveillance and control of infectious diseases must be improved; intensive research into new and emerging diseases, and ways of controlling them, should be encouraged; and public education in food and personal hygiene practices should be intensified.
"Today, infectious diseases are not only a health issue; they have become a social problem with tremendous consequences for the well-being of the individual and the world we live in," said Dr Nakajima. "We need to recognise them as a common threat that has been ignored at great cost for too long and to build the global solidarity to confront them."