Global Burden of Disease - Diarrhea

While diarrhea occurs all over the world, certain regions of the globe are especially affected by this disease. Beyond discomfort, embarrassment, or interruption, diarrheal diseases affect millions of people every year and have serious consequences.

Impact

According to World Health Organization (WHO) estimates for 2004, over 8.9% of deaths in Africa and almost 4.5% in Southeast Asia were caused by diarrheal diseases^[1] Comparing this to 0.41% in Europe^[1]during that same timeframe, it is clear that diarrheal diseases have huge impact in developing parts of the world.

A method used to understand the weight of this disease considers “Disability Adjusted Life Years” or DALYs. A DALY provides a way of measuring the health of a population beyond numbers of deaths – it considers factors such as the loss of healthy years because of disability. The components of a DALY are Years of Life Lost (YLL) to premature death and Years Lost to Disability (YLD). For instance, a DALY measurement for an older person who gets a disease for a short period of time will be smaller than the DALY measurement for a young person who gets a same disease for a longer period of time. Adding up all the DALYs for every person who gets the disease/disability or dies will give an overall picture of the population’s health.

Using DALYs, diarrheal diseases were responsible for a total of 72,777,000 years lost in 2004^[1] Compared to 33,976,000 years lost due to malaria1, diarrheal disease is clearly responsible for a huge loss of healthy years of life. This discrepancy indicates that years of life lost due to diarrheal diseases are more common in young children, as their premature death means loss of more years of potential life. In fact in 2004, more than 1.7 million children under the age of 5 died due to diarrheal diseases ^[1].

Treatments

Treatment of diarrhea has taken various forms over the course of history, including the use of coconut milk- and rice milk-based elixirs. While these treatments were sometimes effective, deaths from dehydration due to diarrhea were still extremely high.

In the mid-1920’s, a relatively safe and effective, though expensive, treatment was discovered – intravenous (through the vein) rehydration^[2] Unfortunately, because people had to be at a hospital to receive the treatment, many people were unable to access it.

Finally in the late 1940’s, scientists realized that people with chronic diarrhea were losing electrolytes (such as potassium and sodium), and more effective intravenous and oral treatments were developed to replenish the body^[2] In the 1970’s, scientists developed the precursor to today’s Oral Rehydration Therapy.

Oral Rehydration Therapy

After much modification, the modern day Oral Rehydration Therapy (ORT) was developed, with the newest formulation released in 2002. The solution is a very simple, and can be made at home with the correct proportions of salt, sugar, and water to prevent dehydration. Other potential at-home fluids include salted rice water or chicken soup with salt. Once dehydration occurs, however, it’s recommended to switch to an official Oral Rehydration Salt (ORS).

Currently manufactured packets of ORS (which are then dissolved in water) contain sodium chloride, glucose, potassium chloride, and trisodium nitrate. These packets cost around 10 cents each, and yield 1 Liter of solution^[3]

Oral Rehydration Therapy is remarkable because it can be administered at home, and can be delivered to remote regions that do not have easy hospital access. However, there are still barriers to success, and the coverage rates for ORT remains below 50%4, meaning there are a lot of cases of diarrhea and dehydration that go untreated by ORT. Though some countries are already manufacturing the ORS locally, in some cases, countries must make national policy changes to promote proper manufacturing, appropriate budgeting, etc.^[4]

Water, Sanitation, Hygiene and Diarrhea

It is likely that the fraction of diarrhea attributable to Water, Sanitation and Hygiene ranges between 70 and 90%. This is due to the fact that even with only 2% of inadequately disposed excreta, the level of faecal-oral pathogens in the environment is likely to be high enough that water, sanitation and hygiene play the dominant role in disease transmission.^[5]

^[2] Access to improved water and sanitation services are, for many countries, are available in the WHO/UNICEF global assessment for the year 2000 (WHO/UNICEF 2000): http://www.who.int/water_sanitation_health/monitoring/en/index.html

Health hazards and risk factors related to water, sanitation and hygiene (WSH) are of a composite nature. Various determining aspects may need to be taken into consideration, including:

• drinking-water is a medium that can serve to transmit pathogens and toxic chemicals;
• the lack of services to provide access to safe drinking-water and adequate sanitation, and the lack of solid waste management services increase the risk of several diseases;
• the failure to apply integrated water resources management principles in the planning, design and operation of dams, irrigation schemes and other hydraulic projects may result in changes in
• water ecologies that lead to the proliferation of the vectors of certain diseases (e.g. malaria, schistosomiasis, lymphatic filariasis, arbovirus infections);
• water-associated behaviors including personal and domestic hygiene, water contact patterns, and unsafe use of built environments are essential to everyday life; and
• the management of aquatic ecosystems may increase or decrease disease risks^[5]

Diseases related to unsafe water

The overall disease burden related to unsafe WSH was first examined at a global level in 1990 ^[6],and was limited to diarrheal diseases. This estimate was revised in 2002 (WHO 2002; Prüss et al, 2002; Prüss-Üstün et al. 2004) based on a systematic and transparent method. Other estimates have since been performed, based on the same method. ^[7] More recently, the impact of WSH on disease has been reassessed in a more comprehensive way (WHO 2007), which estimated that almost one tenth of the global burden of disease can be attributed to WSH. Systematic literature reviews of the association between vector-borne disease burdens and water resources development were commissioned by WHO in 2004 from the Swiss Tropical Institute and showed that, for example for malaria, the vector-borne disease with the highest burden, there are great regional variations in populations at risk of the disease due to proximity of man-made reservoirs and irrigation schemes, and that changes in transmission seasonality and intensity in the wake of water resources development are caused by a complex mixture of contextual determinants.^[8]

WSH-related risks can actually be classified into three broad areas, and each of the areas impacts on certain diseases (although certain diseases are impacted by several groups of interventions). Table 2 illustrates such a grouping.

Table 2 Groups of WSH risks and related diseases

a Certain diseases that are a consequence of malnutrition are also a direct consequence of WSH. For the purpose of calculations, and in order to avoid an overestimate, those diseases are included only once as direct consequence of WSH, and not again as a consequence of malnutrition (this concerns diarrhoeal diseases, malaria, schistosomiasis, lymphatic filariasis, onchocerciasis, dengue, Japanese encephalitis, trachoma and intestinal nematode infections).^[5]

References

1. ↑ ^{1.0 1.1 1.2 1.3} WHO Global Burden of Disease Database http://www.who.int/healthinfo/global_burden_disease/estimates_regional/en/index.html
2. ↑ ^{2.0 2.1 2.2} Ruxin, Joshua Nalibow (1994). “Magic bullet: the history of oral rehydration therapy.” (pdf). Medical History 38 (4): 363–397. PMID 7808099. PMC pmc1036912. Retrieved 2010-03-29.
3. ↑ http://rehydrate.org/ors/index.html
4. ↑ http://www.scielosp.org/scielo.php?pid=S0042-96862009001000014&script=sci_arttext
5. ↑ ^{5.0 5.1 5.2} Water, sanitation and health electronic library [electronic resource] / produced by WHO Water, Sanitation [Geneva, Switzerland] ; World Health Organization, [2008]
6. ↑ Murray, C.J.L. and Lopez, A.D. (1996a) The Global Burden of Disease and Injury Series. Volume I. The Global Burden of Disease. A comprehensive assessment of mortality and disability from diseases, injuries, and risk factors in 1990 and projected to 2020. Harvard School of Public Health, World Bank, World Health Organization.
7. ↑ Cairncross S, Valdmanis V. Water supply, sanitation and hygiene promotion (2006) In: Disease control priorities in developing countries, eds: Jamison D et al. 2nd ed. Oxford University Press and World Bank, Washington.
8. ↑ Keiser J, Utzinger J (2005). Food-borne trematodiasis: an emerging public health problem. Emerging Infectious Diseases, 11 (10): 1503-1510.