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Report of the Workgroup on Noninfectious Diseases
The Workgroup on Noninfectious Diseases recognized that the strategies for eradication and elimination of infectious diseases would need to be revised when applied to noninfectious diseases. The group divided itself into four subgroups to discuss the following: 1) a conceptual framework for eradication/elimination strategies as applied to noninfectious diseases, 2) toxic exposures, 3) protein-energy malnutrition, and 4) micronutrient malnutrition.
The group noted that the definition for "eradication" from the Dahlem Workshop -- "zero cases, zero risk, cessation of intervention" -- would not apply to noninfectious diseases. The conditions considered for eradication so far have been diseases or "portions of diseases" that have a single cause (e.g. cases of acute flaccid paralysis caused by poliovirus). Some noninfectious diseases (e.g. certain toxic exposures) may qualify for eradication because they have a single cause which could be removed completely (e.g. 2-naphthylamine-induced cancer). However, most noninfectious diseases (e.g. resulting from nutritional deficiency) cannot be "eradicated" because the intervention measures must be continued to ensure that the deficiencies do not recur.
The group recognized that there would be difficulty in the strict application to noninfectious diseases of the term "elimination", defined as "zero cases, continuing risk, continuing intervention". For example, micronutrient supplementation, when given to a population with different levels of nutritional adequacy, may not help those with severe deficiency. Furthermore, fluctuations in the adequacy of the diet and supplementation could lead to a rise in cases periodically. However, the group felt that the use of "elimination", despite the technical definition, in relation to nutritional deficiencies and other noninfectious diseases deserved some consideration because of its value as a communications and political tool for rallying enthusiasm, resources and support.
Because noninfectious diseases do not fit the strict definition for candidate diseases to be eradicated or eliminated, the group agreed that other criteria were necessary in setting priorities and in competing for resources. These criteria include burden of disease, cost-effectiveness of interventions, political commitment, and social acceptability which, the group emphasized, had to be considered regardless of whether a disease could be eradicated or eliminated.
Facilitating and Mitigating Factors
The Workgroup considered that one important factor affecting the success of disease control efforts is the degree of interdependence among communities in terms of community interventions. This interdependence appeared to be less for noninfectious than for infectious diseases. For example, the failure of one community to control nutritional deficiencies in its population did not necessarily result in a negative impact on the incidence of disease in a neighbouring community. In contrast, failure of poliomyelitis eradication in one country may pose a continuing risk to its neighbours. For occupational and environmental diseases, exposures in one community may affect health in another community (e.g. a worker taking home a toxin on his contaminated clothing, or a toxin from a factory affecting distant, downwind communities). In comparison to infectious diseases, the relative lack of international interdependence concerning noninfectious diseases may provide greater latitude for one country to select its own health priorities unfettered by the health situation of others. However, the lower degree of interdependence among communities might result in weaker external support.
Another factor affecting the implementation of programmes for noninfectious diseases, which was emphasized, is that the resources from the health system budget to sustain interventions for some noncommunicable diseases (e.g. micronutrient deficiencies) may be reduced after resources from other sectors are tapped. For example, once the private sector has begun iodizing salt and the distribution systems are in place to make it universally available in a country, the need for iodine supplementation campaigns would diminish. Furthermore, given that a nutritional intervention (e.g. salt iodization) is safe, effective and generally applicable, and also that the disease (e.g. iodine deficiency) is noncommunicable, highly sensitive and specific surveillance systems would be less critical than would be the case for the elimination or eradication of a communicable infectious disease.
The group concluded that three issues are critical when considering eradication and elimination strategies for noninfectious diseases: 1) the enormous diversity of these diseases -- each one must be evaluated according to its own characteristics; 2) national health priorities -- these have to be evaluated and interventions need community acceptance within the cultural context of each country; and 3) the need for interventions for proven effectiveness -- countries and donors will be unlikely to invest in interventions that cannot be shown to be effective.
The subgroup recognized the long tradition of successful international efforts to control specific occupational and environmental exposures and national efforts to control other exposure hazards. Examples of international elimination of exposure include phosphorus in the manufacture of matches, and certain synthetic organic dyes that cause bladder cancer; successful national efforts have eliminated silicosis among workers engaged in sandblasting.
As the number of potential toxic-agent candidates for elimination is large and the selection of candidate exposures is difficult, three general points were considered. First, because of uncertainty in the extent of exposure to toxic agents, the number of individuals exposed worldwide to selected occupational and environmental toxins had to be properly estimated. Second, correct estimates had to be made about the number of incident and prevalent cases. Third, exposures resulting in high rates of diseases, albeit in relatively small populations (e.g. certain synthetic specialty chemicals), were considered to qualify as candidates, as well as other toxins that affect large numbers of people (e.g. silica and asbestos).
The occupational and environmental exposures that were considered varied in the magnitude of related cases, evidence of preventability either at particular worksites or countrywide, and the reliability of the known exposure and morbidity statistics about each condition. Considering all these factors, the group recommended two initial candidates for global elimination: lead poisoning and silicosis, because of their seriousness, the existence of a substantial fund of knowledge about these exposures, and the demonstration of control at national level, in the case of silicosis, resulting from a previous WHO commitment to this problem.
Lead poisoning affects both children and workers. An impressive body of data exists on the adverse health effects of lead poisoning, especially in children, even at very low levels of exposure (as low as 10 (g/dl). The negative impact of lead exposure on the cognitive development of children argues for the integration of lead poisoning prevention with comprehensive programmes to prevent mental impairment (e.g. prevention of iodine deficiency and iron deficiency). This argument is further enhanced by the fact that adequate levels of iron and calcium reduce lead uptake in the gut.
Various interventions have effectively reduced or eliminated lead poisoning from paint and additives in fuel, exposure from radiator and battery repairs, etc. Several countries have effectively controlled, if not eliminated, occupational and environmental lead poisoning. Models for lead poisoning prevention exist in the successful programmes in the USA and certain northern European countries (principally Scandinavia), which have reduced blood lead levels in the general population, especially young children, and in occupationally exposed adults.
Techniques for the determination of lead in blood and in the environment are well established in the developed world, but need to be established globally along with quality assurance networks. Recent availability of rugged, low-cost, easy-to-operate lead measurement devices make assessment of human lead exposure feasible in a variety of settings. Effective treatments (succimer and EDTA) are available for children with elevated blood lead levels.
The strategies outlined below were recommended.
Silicosis is a well-known fibrogenic lung disease caused by exposure to crystalline quartz silica dust in sandblasting, rock drilling, tunnelling, and other circumstances. WHO estimates that hundreds of thousands of miners and workers engaged in hazardous industrial occupations are currently affected. Exposure to silica can be controlled by the use of substitute agents and dust control measures. Other factors facilitating control include the availability of medical screening and diagnostic tests as well as environmental measuring devices. Effective control has already been demonstrated in some countries. WHO and ILO have announced a global programme for the elimination of occupationally related silicosis.
Key strategies for the elimination of silicosis include the following: substitution of nonhazardous alternatives in abrasive blasting; use of effective engineering devices to suppress dust and provide ventilation; use of effective personal protective equipment when engineering controls do not suffice; periodic monitoring of the work environment for compliance with protective exposure level; and periodic medical surveillance examinations. Research needs include: design and evaluation of health education programmes, training programmes, and technical information for employers and employees; design and testing of economically acceptable engineering controls for local exposure situations; and development of inexpensive methods of real-time exposure measurement and monitoring.
Considering the complex nature of protein-energy malnutrition, the Workgroup could not recommend it as a candidate disease for elimination. However, given its burden in developing countries, a call was made to renew the commitment of governments to further reduce the levels of malnutrition. Indexed by underweight,** malnutrition affected 29% of less than 5-year-olds in developing countries in 1995, a decline of 34% from a decade earlier (1).
The group noted that to be successful, programmes must address the multiple causes of malnutrition. The immediate causes are inadequate dietary intake and infection, such as diarrhoeal diseases. Generally, there are problems with both the quantity and quality of foods consumed and these result in multiple deficiencies, notably in energy, protein, and micronutrients such as vitamin A, iodine, iron and zinc. The strategies for preventing malnutrition are well known and include: promoting exclusive breastfeeding for the first 4-6 months of life, and its continuation into the second year; improving complementary feeding of children aged 6-24 months; preventing childhood infections such as diarrhoea which lead to poor nutrient utilization and are a cause of poor appetite; improving the availability of food in the household (food security); providing environmental sanitation and personal hygiene; making health services available; and improving the status and education of women in society.
The group noted that the rates of malnutrition have declined rapidly in countries that have reduced poverty and invested heavily in the social sector (e.g. in health, nutrition, and education). As shown in the developed countries, elimination of malnutrition as a public health problem in developing countries can be attained through sustained and equitable economic growth, increased investments in the social sector, and effective programmes that can reduce malnutrition at an accelerated rate. While much is known about preventing malnutrition in children, there is a need for applied research to improve the effectiveness of nutrition programmes.
The Workgroup noted multiple benefits of addressing several micronutrient deficiencies simultaneously. One particular benefit was increasing the efficiency of delivery. Interactions between micronutrients can facilitate uptake, as in the case where the adequacy of vitamin A improves the utilization of iron. In addition, adequate levels of vitamin A and iron enhance the immune response. In turn, the adequacy of iron reduces the tendency to absorb lead.
The group noted that the experience of many countries has shown supplementation and fortification of foods to be efficacious and effective in reducing micronutrient deficiencies. The group proposed recommendations for the elimination of four micronutrient deficiencies: iodine deficiency (by the year 2000); vitamin A deficiency (by 2005); iron deficiency (by 2010); and folic-acid-preventable birth defects (by 2005). Key discussion points are summarized in Table 1.
The conclusions and recommendations are shown below.
Thanks are due to Stephen Corber, William Halperin, Reynaldo Martorell, Shirley Beresford, and Robert Baldwin for their special contributions to this report.
* Vice President, Medical Services Division, Aetna Health Care, Inc., Makati City, Philippines.
** Underweight is a weight two or more standard deviations below the age- and sex-specific mean in the international reference population used by the U.S. National Center for Health Statistics and WHO. About 2.3% of cases are found below this criterion in the reference curve.
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TABLE 1. Determinants for the global elimination of selected micronutrient deficiencies
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