Infections old and new

24 World Health • 48th Y eor, No. 2, March-Aprill995 Infections old and new James W. LeDuc 1 t seems that almost every day newspapers, radio or television have another story either of a new disease never before known to med- ical science or of an old scourge like tuberculosis or cholera reappearing to rernind us that infectious diseases are stiJl very much among us. The growing threat of new, emerging, and re-emerging infectious diseases has long concemed medical science and has now reached the attention of the general public. In response to this ground-swell of concern, WHO began in 1994 a novel programme on new and emerg- ing infectious diseases, based on the Organization's existing commitments to HIV/AIDS, tuberculosis and other prorninent infectious diseases which are on the rise globally. Working with various national agencies, non- governmental organizations and donors, WHO is carrying out a global plan to tackle emerging infectious diseases. What are the causes of this new phenomenon? Changes in lifestyle head the list. Population growth and massive ln 1994, WHO begon a novel programme on new, emergmg and re-emerging infectious diseases. Based on global surveillance, it should ensure thot eor/y warning is given in time to respond to any new threat to public health. infectious diseases and a spawning grou nd for the emergence of new ones. As population pressures grow and resources dwindle, people are increasingly expanding into what were once remote areas where they are increasingly exposed to exotic in- fectious agents. As a result, diseases once thought to be rare may thrive on the newly introduced human hasts . An example is Oropouche fever, a disease known from only a few isolated cases in northem South America and the Caribbean. New settlements in the Amazon Basin have been followed by a proliferation of the insect vector for this virus , which now regularly causes big out- breaks of Oropouche fe ver in the are a. Diseuses thattravel International travel was once the exclusive right of diplomats and the rich. Today Europeans and North Americans think nothing of holiday- ing in Asia or Africa, while residents from the tropics go sightseeing in the temperate zones. Infectious diseases, like people, travel the globe with the airlines, so that a persan infected in one place may become ill in qui te another, and in the process may seed a new outbreak. The rnixing of pathogens that once took months now occurs in days or even hours. Fierce competition in the fast- food industry has obliged producers to bulk process the ingredients, so that the meat used in a hamburger is a mixture, not from one or two cows but from a large number of animais. A single infected animal could thus contaminate liter- ally thousands of hamburgers. If these hamburgers are not fully cooked, there is an obvious poten- tial for massive foodborne out- breaks. A recent outbreak of bloody diarrhoea in severa! states in the USAwas traced to fast-food hamburgers. movement of peo- ple from country areas to alread y over-crowded cities have led to the growth of peri- urban slums where thousands of people live under unhygienic conditions. Such rural to urban migrations world- wide have out- paced supplies of dean water and adequate housing, thus establishing a human reservoir of many known Peri·urban slums, where people live in unhygienic conditions, are reservoirs of infectious diseoses, old and new. Organisms most able to adapt to changing envi- World Health • 48th Y eor, No. 2, Morch-Aprill995 Screening water samples for pathogens . lnfectious disease suNeillance colis for strict precautions as a matter of routine. The huge volume of international !ravel today means thot outbreaks of diseose con spread from country to country in a matter of hours. ronments are the ones most likely to reproduce and thereby succeed in perpetuating their species. This is true for allliving things, including the pathogens that cause infectious diseases; hence the shift and drift of influenza viruses as well as the development of antimicrobial resist- ance among pathogenic bacteria and parasites . An effective public health pro- gramme is reflected in the absence of disease. Y et today, owing to decreas- ing budgets, we find a near global collapse of routine surveillance for infectious diseases, even in the most developed countries. Public health laboratories may be under-staffed and ill equipped to diagnose even common pathogens, let alone exotic importations ; we may therefore find ourselves unable to recognize poten- tially significant public health problems. Need for surveillance Global populations will continue to grow, people will continue to travel, technology will continue to evolve and microorganisms will continue to mutate and adapt. The only practical point of intervention remains basic public health: surveillance, diagno- sis and response, coupled with good 25 hygiene and sanitation. The WHO strategy for new, emerging and re- emerging infectious diseases focuses on recognizing common pathogens, so that we are weil prepared when something new or unusual appears . Comprehensive surveillance coupled with strong laboratory expertise should give us the early warning necessary to respond. WHO's four goals are: • to strengthen global surveillance of infectious diseases; • to build international infrastruc- ture to recognize, report and respond to new and resurgent disease threats; • to create an applied research programme to focus on practical problems and realistic solutions; • to reinforce disease prevention and control through targeted interventions. The project is still developing, but sorne earl y accomplishments include regional and local projects to reduce urban mosquitos, especially Aedes aegypti, the vector of both yellow fever and dengue viruses. Efforts are also under way to prepare and distribute diagnostic reagents to assist in recognizing sorne less common virus diseases. Networks of collaborating centres are being established to strengthen disease surveillance and to share the information obtained. Specifie training activities have started in less developed countries to improve laboratory capacity and strengthen surveillance. And a computer-based network is in place to monitor trends in antimicrobial sensitivity. Strategies to deal with new, emerging and re-emerging infectious diseases focus on ensuring that local health officiais can recognize unusual disease events and are able to invoke preventive measures to limit their spread and impact on society. Above all, national, regional and international cooperation is needed to face this challenge. • Or James W. LeDuc is Medical Officer with the Programme on Bacterial, Viral Oiseases and lmmunology, World Health Organization, 1 2 1 1 Geneva 27, Switzerland