"EPIDEMICS: PROPERTIES, SURVEILLANCE, AND EARLY
WARNINGS"
In the 1970s many experts thought that the fight against infectious diseases was over. Indeed, complacency about the threat of communicable diseases in the 1970s led to less priority for communicable disease surveillance systems. Partly as a result, these systems were not maintained in large parts of the developing world, and this retarded recognition of the magnitude of problems posed by new and re-emerging communicable diseases, and therefore effective action to control them.
During the last two decades, this opinion has been reversed, and there is now a renewed appreciation of the importance of communicable disease. Rapid change is one of the hallmarks of current times. This includes rapidly changing environments for microbes as well as humans. For example, there has been unprecedented population growth, accompanied by rapid, unplanned urbanization. This has resulted in large increases in urban slums without adequate water and waste management. In addition many of the people living in slums are migrants from rural areas, with little immunity to urban diseases. Civil unrest and war contribute to the spread of infectious disease. These changes create an excellent environment for communicable diseases to flourish. The spread of new diseases such as HIV/AIDS, hepatitis C, and dengue haemorrhagic fever, and the resurgence of diseases long since considered under control such as malaria, tuberculosis, cholera, and sleeping sickness, have drawn considerable attention. Infectious diseases cause 63% of all childhood deaths and 48% of premature deaths. There are continuing threats of large epidemics with widespread mortality like the 'Spanish flu' epidemic in 1918-1919 which killed an estimated 40 million people worldwide, or the HIV/AIDS epidemic which has caused widespread morbidity and mortality, and reversed hard-won gains in life expectancy in Africa.
In this modern world, with increased globalization,
and rapid air travel, it is clear that effective public health surveillance
is critical for the early detection and prevention of epidemics, and international
coordination and collaboration is of paramount importance. There is an
urgent need for surveillance of (i) known existing communicable diseases,
especially those with high epidemic potential, (ii) early recognition of
new infections (over 20 new pathogens have been discovered since the mid-1970s),
and (iii) monitoring the growing resistance to antimicrobial drugs.
Detection and reporting of pathogens is very important
for all infectious diseases. For some diseases, such as influenza, new
strains occur frequently. For influenza, a major component of surveillance
is to track circulating virus strains, which is key for the development
of appropriate influenza vaccines each year. Dengue is another disease
where particular importance is given to keeping track of circulating virus
strains to assess the potential for outbreaks of dengue haemorrhagic fever.
Surveillance of pathogens relies on laboratory analysis both for the confirmation
of clinical diagnoses, and for the assessment of antimicrobial resistance.
In the absence of a correct diagnosis, the implementation of appropriate
treatment, control and prevention measures are seriously hampered, particularly
in the case of unforeseen outbreaks. Good surveillance requires strong
laboratory facilities, appropriate resources both human and financial,
access to necessary reagents, and strong quality control.
It is becoming increasingly evident that geographic information systems (GIS) and related mapping technologies represent very powerful resource tools within the context of public health programming. The use and implementation of GIS for public health applications at country level has significantly expanded. Over recent years, significant progress has been made in this domain, and from district to global levels, GIS and mapping is being used by a wide range of public health programmes including health & nutrition, water & sanitation, education and emergencies. This has been facilitated by the rapid expansion of data distribution channels through the World Wide Web, modems and also through the introduction of more user-friendly low cost mapping tools. Combinations of these techniques with remote data sensing and remote data entry, which are currently being evaluated, will bring further improvements in speed of detection, management and control of epidemics in the future. It is also hoped that outbreaks will be predictable in some instances, allowing for specific preventive actions.
The interest and participation in geographic information system development and mapping within health and other sectors is now shared by many different programmes from different UN agencies including WHO, UNICEF, UNAIDS, UNFPA and other agencies or public health institutions such as INSERM (France) and NASA.
Key strategic objectives for the next future are:
These objectives are in line with WHO's role
to ensure international coordination of epidemic response, particularly
for diseases of international public health importance or when countries
lack the capacity to respond to an epidemic themselves. The goal is to
ensure the application of the best available methods for the prevention
and control of outbreaks, and the maximum security against the international
spread of diseases with a minimum interference with world traffic.