Chapter 2 summary
Threats to public health security
Chapter 2 explores a range of threats to global public health security, as defined by IHR (2005), which result from human actions or causes, from human interaction with the environment, and from sudden chemical and radioactive events, including industrial accidents and natural phenomena. It begins by illustrating how inadequate investment in public health, resulting from a false sense of security in the absence of infectious disease outbreaks, has led to reduced vigilance and a relaxing of adherence to effective prevention programmes.
For example, following the widespread use of insecticides in large-scale, systematic control programmes, by the late 1960s most of the important vector-borne diseases were no longer considered major public health problems outside of sub-Saharan Africa. Control programmes then lapsed as resources dwindled. The result was that within the next 20 years, many important vector-borne diseases including African trypanosomiasis, dengue and dengue haemorrhagic fever, and malaria emerged in new areas or re-emerged in areas previously affected. Urbanization and increasing international trade and travel have contributed to rapid spread of dengue viruses and their vectors. Dengue caused an unprecedented pandemic in 1998, with 1.2 million cases reported to WHO from 56 countries. Since then, dengue epidemics have continued, affecting millions of people from Latin America to South-East Asia. Globally, the average annual number of cases reported to WHO has nearly doubled in each of the last four decades.
Inadequate surveillance results from a lack of commitment to build effective health systems capable of monitoring a country’s health status. The rapid global emergence and spread of HIV/AIDS in the 1970s illustrates this. The presence of this new health threat was not detected by what were invariably weak health systems in many developing countries. It only belatedly became a matter of international concern with the first cases in the United States. In addition to limited disease surveillance capacity and data, early efforts to control the AIDS epidemic were also hampered by a lack of solid data on sexual behaviour in African countries, the United States and other industrialized countries. Behavioural data were practically non-existent in the developing world. The understanding of HIV/AIDS in the context of sexuality, gender relations and migration in the developing world took years to develop and is still poorly understood.
Even with reliable operations in place, other influences on public health programmes can have lethal and costly repercussions. Such was the case in August 2003, when unsubstantiated claims originating in northern Nigeria that the oral poliomyelitis vaccine (OPV) was unsafe and could sterilize young children led to the suspension of polio immunization in two northern states and substantial reductions in polio immunization coverage in a number of others. The result was a large outbreak of polio across northern Nigeria and the reinfection of previously polio-free areas in the south of the country. This outbreak eventually paralysed thousands of children in Nigeria and spread from northern Nigeria to 19 polio-free countries.
Chapter 2 also considers the public health consequences of conflicts, such as the outbreak of Marburg haemorrhagic fever against the background of the 1975-2002 civil war in Angola, and the cholera epidemic in the Democratic Republic of the Congo in the aftermath of the crisis in Rwanda in 1994. In July of that year, between 500 000 and 800 000 people crossed the border to seek refuge in the outskirts of the Congolese city of Goma. During the first month after their arrival, close to 50 000 refugees died in a widespread outbreak of combined cholera and shigella dysentery. The speed of transmission and the high rate of infection were related to the contamination with Vibrio cholerae of the only available source of water and the absence of proper housing and sanitation.
The problem of microbial adaptation, the use and misuse of antibiotics and zoonotic diseases, such as human bovine spongiform encephalopathy (BSE) and Nipah virus, is discussed. The history of Nipah virus emergence provides another example of a new human pathogen that originated from an animal source, initially caused zoonotic disease, and subsequently evolved to become a more efficient human pathogen. This trend calls for closer collaboration among sectors responsible for human health, veterinary health and wildlife.
Infectious diseases following extreme weather-related events and the acute public health impact of sudden chemical and radioactive events are also discussed. These now fall within the scope of IHR (2005) if they have the potential to cause harm on an international scale, including the deliberate use of biological and chemical agents, and industrial accidents. Among the examples of accidents given here is the Chernobyl nuclear accident in Ukraine in 1986, which dispersed radioactive materials into the atmosphere over a huge area of Europe. Put together, the examples in this chapter reveal the alarming variety of threats to global health security towards the end of the 20th century.