Overview
Global public health threats in the 21st century
Today’s highly mobile, interdependent and interconnected world provides myriad opportunities for the rapid spread of infectious diseases, and radionuclear and toxic threats, which is why updated and expanded Regulations are necessary. Infectious diseases are now spreading geographically much faster than at any time in history. It is estimated that 2.1 billion airline passengers travelled in 2006; an outbreak or epidemic in any one part of the world is only a few hours away from becoming an imminent threat somewhere else (see Figure 1).
Infectious diseases are not only spreading faster, they appear to be emerging more quickly than ever before. Since the 1970s, newly emerging diseases have been identified at the unprecedented rate of one or more per year. There are now nearly 40 diseases that were unknown a generation ago. In addition, during the last five years, WHO has verified more than 1100 epidemic events worldwide.
The categories and examples given below illustrate the variety and breadth of public health threats confronting people today.
Epidemic-prone diseases
Cholera, yellow fever and epidemic meningococcal diseases made a comeback in the last quarter of the 20th century and call for renewed efforts in surveillance, prevention and control. Severe Acute Respiratory Syndrome (SARS) and avian influenza in humans have triggered major international concern, raised new scientific challenges, caused major human suffering and imposed enormous economic damage. Other emerging viral diseases such as Ebola, Marburg haemorrhagic fever and Nipah virus pose threats to global public health security and also require containment at their source due to their acute nature and resulting illness and mortality. During outbreaks of these diseases, rapid assessment and response, often needing international assistance, has been required to limit local spread. Strengthening of capacity is imperative in the future to assess such new threats.
Gains in many areas of infectious disease control are seriously jeopardized by the spread of antimicrobial resistance, with extensively drug-resistant tuberculosis (XDR-TB) now a cause of great concern. Drug resistance is also evident in diarrhoeal diseases, hospital-acquired infections, malaria, meningitis, respiratory tract infections, and sexually transmitted infections, and is emerging in HIV.
Foodborne diseases
The food chain has undergone considerable and rapid changes over the last 50 years, becoming highly sophisticated and international. Although the safety of food has dramatically improved overall, progress is uneven and foodborne outbreaks from microbial contamination, chemicals and toxins are common in many countries. The trading of contaminated food between countries increases the potential that outbreaks will spread. In addition, the emergence of new foodborne diseases creates considerable concern, such as the recognition of the new variant of Creutzfeldt-Jakob disease (vCJD) associated with bovine spongiform encephalopathy (BSE).
Accidental and deliberate outbreaks
As activities related to infectious disease surveillance and laboratory research have increased in recent years, so too has the potential for outbreaks associated with the accidental release of infectious agents. Breaches in biosafety measures are often responsible for these accidents. At the same time, opportunities for malicious releases of dangerous pathogens, once unthinkable, have become a reality, as shown by the anthrax letters in the United States of America in 2001.
In addition, the recent past has been marked by disturbing new health events that resulted from chemical or nuclear accidents and sudden environmental changes, causing major concerns in many parts of the world.
Toxic chemical accidents
- West Africa, 2006: the dumping of approximately 500 tons of petrochemical waste in at least 15 sites around the city of Abidjan, Côte d’Ivoire, led to the deaths of eight people being attributed to exposure to the waste and to nearly 90 000 more people seeking medical help. Other countries were concerned that they could also have been put at risk as a result of dumping elsewhere or as a result of chemical contamination of transboundary rivers.
- Southern Europe, 1981: 203 people died after consuming poisoned cooking oil that was adulterated with industrial rapeseed oil. A total of 15 000 people were affected by the tainted oil and no cure to reverse the adverse effects of toxic oil syndrome was ever found.
Radionuclear accidents
- Eastern Europe, 1986: the Chernobyl disaster is regarded as the worst accident in the history of nuclear power. The explosion at the plant resulted in the radioactive contamination of the surrounding geographical area, and a cloud of radioactive fallout drifted over western parts of the former Soviet Union, eastern and western Europe, some Nordic countries and eastern North America. Large areas of Ukraine, the Republic of Belarus and the Russian Federation were badly contaminated, resulting in the evacuation and resettlement of over 336 000 people.
Environmental disasters
- Europe, 2003: the heatwave in Europe that claimed the lives of 35 000 persons was linked to unprecedented extremes in weather in other parts of the world during the same period.
- Central Africa, 1986: more than 1700 people died of carbon dioxide poisoning following a massive release of gas from Lake Nyos, a volcanic crater lake. Such an event requires rapid assessment to determine if it is an international threat.
This Overview summarizes some of the above examples, which, together with the lessons drawn from them, are more widely discussed in the report. The report emphasizes that the international response required today is not only to the known, but also to the unknown – the diseases that may arise from acute environmental or climatic changes and from industrial pollution and accidents that may put millions of people at risk in several countries.