See also: Neglected tropical diseases
Diseases of poverty is a term sometimes used to collectively describe diseases, disabilities, and health conditions that are more prevalent among the poor than among wealthier people. In many cases poverty is considered the leading risk factor or determinant for such diseases, and in some cases the diseases themselves are identified as barriers to economic development that would end poverty. Diseases of poverty are often co-morbid and ubiquitous with malnutrition.
These diseases triggered in part by poverty are in contrast to so-called "diseases of affluence", which are diseases thought to be a result of increasing wealth in a society.
For many environmental and social reasons, including crowded living and working conditions, inadequate sanitation, and disproportionate occupation as sex workers, the poor are more likely to be exposed to infectious diseases. Malnutrition, stress, overwork, and inadequate, inaccessible, or non-existent health care can hinder recovery and exacerbate the disease.Malnutrition is associated with 54% of childhood deaths from diseases of poverty, and lack of skilled attendants during childbirth is primarily responsible for the high maternal and infant death rates among the poor.
Each year many children and adults die as a result of a lack of access to clean drinking water and poor sanitation. Many combinable diseases and many of the poverty related diseases spread as a result of inadequate access to clean drinking water. According to UNICEF, 3,000 children die every day, worldwide due to contaminated drinking water and poor sanitation.
Although the Millennium Development Goal (MDG) of halving the number of people who did not have access to clean water by 2015, was reached five years ahead of schedule in 2010, there are still 783 million people who rely on unimproved water sources. In 2010 the United Nations declared access to clean water a fundamental human right, integral to the achievement of other rights. This made it enforceable and justifiable to permit governments to ensure their populations access to clean water. Though access to water has improved for some, it continues to be especially difficult for women and children. Women and girls bear most of the burden for accessing water and supplying it to their households.
In India, Sub-Saharan Africa, and parts of Latin America, women are required to travel long distances in order to access a clean water source and then bring some water home. This has a significant impact on girls’ educational attainment.
There have been further efforts to improve water quality using new technology which allows water to be disinfected immediately upon collection and during the storage process. Clean water is necessary for cooking, cleaning, and laundry because many people come into contact with disease causing pathogens through their food, or while bathing or washing.
Contaminated water and inadequate sanitation are related to diseases of poverty such as malaria, parasitic diseases, and schistosomiasis. These infections act as cofactors that increase the risk of HIV transmission.
Standpipes and sanitation are provided in most developing areas, but the death rates are not significantly reduced. One of the reasons that water-related diseases are still occurring is because water supplies can be contacted by contaminated surface water. To effectively decrease the morbidity and mortality of diseases, the population should get access to water from home instead from outside. Therefore, in addition to the installation of standpipes, water supplies and sanitation should be provided within houses.
Malnutrition disproportionately affect those in sub-Saharan Africa. Over 35 percent of children under the age of 5 in sub-Saharan Africa show physical signs of malnutrition. Malnutrition, the immune system, and infectious diseases operate in a cyclical manner: infectious diseases have deleterious effects on nutritional status, and nutritional deficiencies can lower the strength of the immune system which affects the body’s ability to resist infections. Similarly, malnutrition of both macronutrients (such as protein and energy) and micronutrients (such as iron, zinc, and vitamins) increase susceptibility to HIV infections by interfering with the immune system and through other biological mechanisms. Depletion of macronutrients and micronutrients promotes viral replication that contributes to greater risks of HIV transmission from mother-to-child as well as those through sexual transmission. Increased mother-to-child transmission is related to specific deficiencies in micronutrients such as vitamin A. Further, anemia, a decrease in the number of red blood cells, increases viral shedding in the birth canal, which also increases risk of mother-to-child transmission. Without these vital nutrients, the body lacks the defense mechanisms to resist infections. At the same time, HIV lowers the body’s ability to intake essential nutrients. HIV infection can affect the production of hormones that interfere with the metabolism of carbohydrates, proteins, and fats.
In the United States, 11.1 percent of households struggle with food insecurity. Food insecurity refers to the lack of access to quality food for a healthy lifestyle. The rate of hunger and malnutrition in female headed households was three times the national average at 30.2 percent. According to the Food and Agriculture Organization of the United Nations, 10 percent of the population in Latin America and the Caribbean are affected by hunger and malnutrition.
See also: Social determinants of health in poverty
Poverty and disease are tied closely together, with each factor aiding the other. Many diseases that primarily affect the poor serve to also deepen poverty and worsen conditions. Poverty also significantly reduces people's capabilities making it more difficult to avoid poverty related diseases. The majority of diseases and related mortality in poor countries is due to preventable, treatable diseases for which medicines and treatment regimes are readily available. Poverty is in many cases the single dominating factor in higher rates of prevalence of these diseases. Poor hygiene, ignorance in health-related education, non-availability of safe drinking water, inadequate nutrition and indoor pollution are factors exacerbated by poverty.
The largest three poverty-related diseases (PRDs) — AIDS, malaria, and tuberculosis — account for 18% of diseases in poor countries. The disease burden of treatable childhood diseases in high-mortality, poor countries is 5.2% in terms of disability-adjusted life years but just 0.2% in the case of advanced countries.
In addition, infant mortality and maternal mortality are far more prevalent among the poor. For example, 98% of the 11,600 daily maternal and neonatal deaths occur in developing countries.
Together, diseases of poverty kill approximately 14 million people annually.[dead link]Gastroenteritis with its associated diarrhea results in about 1.8 million deaths in children yearly with most of these in the world's poorest nations.
At the global level, the three primary PRDs are tuberculosis, AIDS/HIV and malaria. Developing countries account for 95% of the global AIDS prevalence and 98% of active tuberculosis infections. Furthermore, 90% of malaria deaths occur in sub-Saharan Africa. Together, these three diseases account for 10% of global mortality.
Treatable childhood diseases are another set which have disproportionately higher rates in poor countries despite the availability of cures for decades. These include measles, pertussis and polio.
Three other diseases, measles, pneumonia, and diarrheal diseases, are also closely associated with poverty, and are often included with AIDS, malaria, and tuberculosis in broader definitions and discussions of diseases of poverty.
Main article: Neglected tropical diseases
Based upon the spread of research in cures for diseases, certain diseases are identified and referred to as "neglected diseases". These include the following diseases:
Tropical diseases such as these tend to be neglected in research and development efforts. Of 1393 new drugs brought into use over a period of 25 years (1975–1999), only a total of thirteen, less than 1%, related to these diseases. Of 20 MNC drug companies surveyed for research on PRDs, only two had projects targeted towards these neglected PRDs. However, the combined total number of deaths due to these diseases is dwarfed by the enormous number of patients affected by PRDs such as respiratory infections, HIV/AIDs, diarrhoea and tuberculosis, besides many others. Similar to the spread of tropical neglected diseases in developing nations, these neglected infections disproportionately affect poor and minority populations in the United States. These diseases have been identified by the Centers for Disease Control and Prevention, as priorities for public health action based on the number of people infected, the severity of the illnesses, and the ability to prevent and treat them.
Trichomoniasis is the most common sexually transmitted infection affecting more than 200 million people worldwide. It is especially prevalent among young, poor and African American women. This infection is also common in poor communities in Sub-Saharan Africa and impoverished parts of Asia. This neglected infection is one of special concern because it is associated with a heightened risk for contracting HIV and pre-term deliveries.
In addition, availability of cures and recent advances in medicine have led to only three diseases being considered neglected diseases, namely, African trypanosomiasis, Chagas disease and Leishmaniasis.
Africa accounts for a majority of malaria infections and deaths worldwide. Over 80 percent of the 300 to 500 million malaria infections occurring annually worldwide are in Africa. Each year, about one million children under the age of five die from malaria. Children who are poor, have mothers with little to no education, and live in rural areas are more susceptible to malaria and more likely to die from it. Malaria is directly related to the spread of HIV in sub-Saharan Africa. It increases viral load seven to ten times, which increases the chances of transmission of HIV through sexual intercourse from a patient with malaria to an uninfected partner. After the first pregnancy, HIV can also decrease the immunity to malaria. This contributes to the increase of the vulnerability to HIV and higher mortality from HIV, especially for women and infants. HIV and malaria interact in a cyclical manner—being infected with malaria increases susceptibility to HIV infection, and HIV infections increase malarial episodes. The co-existence of HIV and malaria infections helps spread both diseases, particularly in Sub-Saharan Africa.Malaria vaccines are an area of intensive research.
Intestinal parasites are extremely prevalent in tropical areas. These include hookworms, roundworms, and other amoebas. They can aggravate malnutrition by depleting essential nutrients through intestinal blood loss and chronic diarrhea. Chronic worm infections can further burden the immune system. At the same time, chronic worm infections can cause immune activation that increases susceptibility of HIV infection and vulnerability to HIV replication once infected.
Schistosomiasis (bilharzia) is a parasitic disease caused by the parasitic flatworm trematodes. Moreover, more than 80 percent of the 200 million people worldwide who have schistosomiasis live in sub-Saharan Africa. Infections often occur in contaminated water where freshwater snails release larval forms of the parasite. After penetrating the skin and eventually traveling to the intestines or the urinary tract, the parasite lays eggs and infects those organs. It damages the intestines, bladder, and other organs and can lead to anemia and protein-energy deficiency. Along with malaria, schistosomiasis is one of the most important parasitic co-factors aiding in HIV transmission. Epidemiological data shows schistosome-endemic areas coincide with areas of high HIV prevalence, suggesting that parasitic infections such as schistosomiasis increase risk of HIV transmission.
Tuberculosis is the leading cause of death around the world for an infectious disease. This disease is especially prevalent in sub-Saharan Africa, and the Latin American and Caribbean region. While the tuberculosis rate is decreasing in the rest of the world, it is increasing by rate of 6 percent per year in Sub-Saharan Africa. It is the leading cause of death for people with HIV in Africa. Tuberculosis (TB) is closely related to lifestyles of poverty, overcrowded conditions, alcoholism, stress, drug addiction and malnutrition. This disease spreads quickly among people who are undernourished. According to the Center for Disease Control and Prevention, in the United States, tuberculosis is more prevalent among foreign born persons, and ethnic minorities. The rates are especially high among Hispanics, Blacks and Asians. HIV infection and TB are also closely tied. Being infected with HIV increases the rate of activation of latent TB infections, and having TB, increases the rate of HIV replication, therefore accelerating the progression of AIDS.
AIDS is a disease of the human immune system caused by the human immunodeficiency virus (HIV). Primary modes of HIV transmission in sub-Saharan Africa are sexual intercourse, mother-to-child transmission (vertical transmission), and through HIV-infected blood. Since rate of HIV transmission via heterosexual intercourse is so low, it is insufficient to cause AIDS disparities between countries. Critics of AIDS policies promoting safe sexual behaviors believe that these policies miss the biological mechanisms and social risk factors that contribute to the high HIV rates in poorer countries. In these developing countries, especially those in sub-Saharan Africa, certain health factors predispose the population to HIV infections.
Many of the countries in Sub-Saharan Africa are ravaged with poverty and many people live on less than one United States dollar a day. The poverty in these countries gives rise to many other factors that explain the high prevalence of AIDS. The poorest people in most African countries suffer from malnutrition, lack of access to clean water, and have improper sanitation. Because of a lack of clean water many people are plagued by intestinal parasites that significantly increase their chances of contracting HIV due to compromised immune system. Malaria, a disease still rampant in Africa also increases the risk of contracting HIV. These parasitic diseases, affect the body’s immune response to HIV, making people more susceptible to contracting the disease once exposed. Genital schistosomiasis, also prevalent in the topical areas of Sub-Saharan Africa and many countries worldwide, produces genital lesions and attract CD4 cells to the genital region which promotes HIV infection. All these factors contribute to the high rate of HIV in Sub-Saharan Africa. Many of the factors seen in Africa are also present in Latin America and the Caribbean and contribute to the high rates of infections seen in those regions. In the United States, poverty is a contributing factor to HIV infections. There is also a large racial disparity, with African Americans having a significantly higher rate of infection than their white counterparts.
More than 300 million people worldwide have asthma. The rate of asthma increases as countries become more urbanized and in many parts of the world those who develop asthma do not have access to medication and medical care. Within the United States, African Americans and Latinos are four times more likely to suffer from severe asthma than whites. The disease is closely tied to poverty and poor living conditions. Asthma is also prevalent in children in low income countries. Homes with roaches and mice, as well as mold and mildew put children at risk for developing asthma as well as exposure to cigarette smoke.
Unlike many other Western countries, the mortality rate for asthma has steadily risen in the United States over the last two decades. Mortality rates for African American children due to asthma are also far higher than that of other racial groups. For African Americans, the rate of visits to the emergency room is 330 percent higher than their white counterparts. The hospitalization rate is 220 percent higher and the death rate is 190 percent higher. Among Hispanics, Puerto Ricans are disporpotionatly affected by asthma with a disease rate that is 113 percent higher than non-Hispanic Whites and 50 percent higher than non-Hispanic Blacks. Studies have shown that asthma morbidity and mortality are concentrated in inner city neighborhoods characterized by poverty and large minority populations and this affects both genders at all ages. Asthma continues to have an adverse effects on the health of the poor and school attendance rates among poor children. 10.5 million days of school are missed each year due to asthma.
Though heart disease is not exclusive to the poor, there are aspects of a life of poverty that contribute to its development. This category includes coronary heart disease, stroke and heart attack. Heart disease is the leading cause of death worldwide and there are disparities of morbidity between the rich and poor. Studies from around the world link heart disease to poverty. Low neighborhood income and education were associated with higher risk factors. Poor diet, lack of exercise and limited (or no) access to a specialist were all factors related to poverty, though to contribute to heart disease. Both low income and low education were predictors of coronary heart disease, a subset of cardiovascular disease. Of those admitted to hospital in the United States for heart failure, women and African Americans were more likely to reside in lower income neighborhoods. In the developing world, there is a 10 fold increase in cardiac events in the black and urban populations.
Obstetric fistula or vaginal fistula is a medical condition in which a fistula (hole) develops between either the rectum and vagina (see rectovaginal fistula) or between the bladder and vagina (see vesicovaginal fistula) after severe or failed childbirth, when adequate medical care is not available. It is considered a disease of poverty because of its tendency to occur women in poor countries who do not have health resources comparable to developed nations.
Dental decay or dental caries is the gradual destruction of tooth enamel. Poverty is a significant determinant for oral health. Dental caries is one of the most common chronic diseases worldwide. In the United States it is the most common chronic disease of childhood. Risk factors for dental caries includes living in poverty, poor education, low socioeconomic status, being part of an ethnic minority group, having a developmental disability, recent immigrants and people infected with HIV/AIDS. In Peru, poverty was found to be positively correlated with dental caries among children. According to a report by U.S health surveillance, tooth decay peaks earlier in life and is more severe in children with families living below the poverty line. Tooth decay is also strongly linked to dietary behaviors, and in poor rural areas where nutrient dense foods, fruits and vegetables are unavailable, the consumption of sugary and fatty food increases the risk of dental decay. Because the mouth is a gateway to the respiratory and digestive tracts, oral health has a significant impact on other health outcomes. Gum disease has been linked to diseases such as cardiovascular disease.
Diseases of poverty reflect the dynamic relationship between poverty and poor health; while such diseases result directly from poverty, they also perpetuate and deepen impoverishment by sapping personal and national health and financial resources. For example, malaria decreases GDP growth by up to 1.3% in some developing nations, and by killing tens of millions in sub-Saharan Africa, AIDS alone threatens “the economies, social structures, and political stability of entire societies”.
Women and children are often put at a high risk of being infected by schistosomiasis, which in turn puts them at a higher risk of acquiring HIV. Since the mode of schistosomiasis transmission is usually through contaminated water in streams and lakes, women and children who do their household chores by the water are more likely to acquire the disease. Activities that women and children often do around waterfront include washing clothes, collecting water, bathing, and swimming. Women who have schistosomiasis lesions are three times more likely to be infected with HIV.
Women also have a higher risk of HIV transmission through the use of medical equipment such as needles. Because more women than men use health services, especially during pregnancy, they are more likely to come across unsterilized needles for injections. Although statistics estimate that unsterilized needles only account for 5 to 10 percent of primary HIV infections, studies show this mode of HIV transmission may be higher than reported. This increased risk of contracting HIV through non-sexual means has social consequences for women as well. Over half of the husbands of HIV-positive women in Africa tested HIV-negative. When HIV-positive women reveal their HIV status to their HIV-negative husbands, they are often accused of infidelity and face violence and abandonment from their family and community.
Relating to human capabilities
Malnutrition associated with HIV impacts people’s ability to provide for themselves and their dependents, thus limiting the human capabilities of both themselves and their dependents. HIV can negatively affect work output, which impacts the ability to generate income. This is crucial in parts of Africa where farming is the primary occupation and obtaining food is dependent on the agricultural outcome. Without adequate food production, malnutrition becomes more prevalent. Children are often collateral damage in the AIDS crisis. As dependents, they can be burdened by the illness and eventual death of one or both parents due to HIV/AIDS. Studies have shown that orphaned children are more likely to display physical symptoms of malnutrition than children whose parents are both alive.
Public policy proposals
There are a number of proposals for reducing the diseases of poverty and eliminating health disparities within and between countries. The World Health Organization proposes closing the gaps by acting on social determinants. Their first recommendation is to improve daily living conditions. This area involves improving the lives of women and girls so that their children are born in healthy environments and placing an emphasis on early childhood health. Their second recommendation is to tackle the inequitable distribution of money, power and resources. This would involve building stronger public sectors and changing the way in which society is organized. Their third recommendation is to measure and understand the problem and assess the impact of action. This would involve training policy makers and healthcare practitioners to recognize problems and form policy solutions.
- Nutrition Supplements: Focusing on reversing the pattern of malnutrition in sub-Saharan African and other poor countries is a one possible way of decreasing susceptibility to HIV infections. Micronutrients such as iron and vitamin A can be delivered and provided at a very low cost. For example, vitamin A supplements cost $0.02 per capsule if provided twice a year. Iron supplements per child cost $0.02 if provided weekly or $0.08 if provided daily.
- Eliminating Cofactors: Tackling the very diseases that increase risk of HIV infections can help slow down the rates of HIV transmission. Cofactors such as malaria and parasitic infections can be combated in an effective and cost-efficient manner. For example, mosquito nets can be easily used to prevent malaria. Parasites can be eliminated with medication that is cost-effective and easy to administer. Twice-yearly treatments range from $0.02 to $0.25 depending on the type of worm.
- ^ abcdeSingh, A. R., & Singh, S. A. (2008). Diseases of Poverty and Lifestyle, Well-Being and Human Development. Mens Sana Monographs, 6(1), 187-225.
- ^"Health and Poverty". UNFPA State of World Population 2002. United Nations Population Fund.
- ^ abWHO | Ensuring skilled care for every birth.Archived December 6, 2011, at the Wayback Machine.
- ^WHO | Goal 4: reduce child mortalityArchived August 20, 2009, at the Wayback Machine.
- ^ abUNICEF (Water).Archived April 9, 2008, at the Wayback Machine.
- ^ abSingh, Nandita, Per Wickenberg, Karsten Åström, and Håkan Hydén. 2012. "Accessing water through a rights-based approach: problems and prospects regarding children." Water Policy 14, no. 2: 298-318.
- ^Access to Clean Water and Sanitation Pose 21st-Century Challenge for Millions" JAMA 2004;292(3) 318-320. doi:10.1001/jama.292.3.318
- ^Mintz, E., Reiff, F., & Tauxe, R. (1995). Safe water treatment and storage in the home. A practical new strategy to prevent waterborne disease. JAMA: The Journal of the American Medical Association, 273(12), 948-953.
- ^"Common water and sanitation-related diseases". UNICEF. 2005.
- ^ abcdefghijklmStillwaggon, Eileen (2008). "Race, Sex, and the Neglected Risks for Women and Girls in Sub-Saharan Africa". Feminist Economics. 14 (4): 67–86. doi:10.1080/13545700802262923.
- ^Walsh, Julia A., and Kenneth S. Warren. 1980. Selective primary health care: An interim strategy for disease control in developing countries. Social Science & Medicine. Part C: Medical Economics 14 (2):145-163.
- ^ abcdefPiwoz, Ellen G.; Preble, Elizabeth A. (December 2000). "HIV/AIDS and Nutrition: A Review of the Literature and Recommendations for Nutritional Care and Support in Sub-Saharan Africa"(PDF). Washington DC: Academy for Educational Development. PN-ACK-673.
- ^Friis H, Michaelsen KF (March 1998). "Micronutrients and HIV infection: a review". Eur J Clin Nutr. 52 (3): 157–63. doi:10.1038/sj.ejcn.1600546. PMID 9537299.
- ^ abSemba RD, Miotti PG, Chiphangwi JD, et al. (June 1994). "Maternal vitamin A deficiency and mother-to-child transmission of HIV-1". Lancet. 343 (8913): 1593–7. doi:10.1016/S0140-6736(94)93056-2. PMID 7911919.
- ^Nimmagadda A, O'Brien WA, Goetz MB (March 1998). "The significance of vitamin A and carotenoid status in persons infected by the human immunodeficiency virus". Clin. Infect. Dis. 26 (3): 711–8. doi:10.1086/514565. PMID 9524850.
- ^John GC, Nduati RW, Mbori-Ngacha D, et al. (January 1997). "Genital shedding of human immunodeficiency virus type 1 DNA during pregnancy: association with immunosuppression, abnormal cervical or vaginal discharge, and severe vitamin A deficiency". J. Infect. Dis. 175 (1): 57–62. doi:10.1093/infdis/175.1.57. PMC 3372419. PMID 8985196.
- ^ abChilton, M. (2009). A Rights-Based Approach to Food Insecurity in the United States. American Journal of Public Health, 99(7), 1203.
- ^Freeing Latin America and the Caribbean from hungerArchived September 18, 2011, at the Wayback Machine..
- ^ abcdefgStevens, Philip (November 2004). "Diseases of Poverty and the 10/90 gap"(PDF). International Policy Network. Retrieved 20 March 2012.
- ^ abRESULTS: World Health/Diseases of Poverty.Archived July 3, 2009, at the Wayback Machine.
- ^Dolin, [edited by] Gerald L. Mandell, John E. Bennett, Raphael (2010). Mandell, Douglas, and Bennett's principles and practice of infectious diseases (7th ed.). Philadelphia, PA: Churchill Livingstone/Elsevier. ISBN 0443068399.
- ^ abWHO/WPRO-Poverty Issues Dominate RCMArchived April 3, 2011, at the Wayback Machine.
- ^"HIV/AIDS and Poverty". UNFPA State of World Population 2002. United Nations Population Fund.
- ^Roll Back Malaria Partnership: What is malaria?Archived April 23, 2006, at the Wayback Machine.
- ^World Health/Diseases of Poverty. Retrieved 05 January 2016.
- ^Hotez PJ (2008) Neglected Infections of Poverty in the United States of America.PLoS Negl Trop Dis 2(6):e256.doi:10.1371/journal.pntd.0000256
- ^Centers For Disease Control.Archived May 11, 2016, at the Wayback Machine.
- ^Ko, H., Jamieson, D. J., Hogan, J. W., Anderson, J., Klein, R. S., Susan, C., & Paula, S. (2002). Prevalence, Incidence, and Persistence or Recurrence of Trichomoniasis among Human Immunodeficiency Virus (HIV)-Positive Women and among HIV-Negative Women at High Risk for HIV Infection" Clinical Infectious Diseases 34(10), 1406-1411.
- ^Crosse, M. (2005). Global malaria control [electronic resource] : U.S. and multinational investments and implementation challenges. Washington, DC : U.S. Government Accountability Office, .
- ^Malaria. World Health Organization (WHO). 2004.[permanent dead link] Retrieved March 2011.
- ^Ingstad, B., Munthali, A., Braathen, S., & Grut, L. (2012). The evil circle of poverty: a qualitative study of malaria and disability. Malaria Journal, 1115.
- ^Whitworth J, Morgan D, Quigley M, et al. (September 2000). "Effect of HIV-1 and increasing immunosuppression on malaria parasitaemia and clinical episodes in adults in rural Uganda: a cohort study". Lancet. 356 (9235): 1051–6. doi:10.1016/S0140-6736(00)02727-6. PMID 11009139.
- ^Hoffman IF, Jere CS, Taylor TE, et al. (March 1999). "The effect of Plasmodium falciparum malaria on HIV-1 RNA blood plasma concentration". AIDS. 13 (4): 487–94. doi:10.1097/00002030-199903110-00007. PMID 10197377.
- ^Rowland-Jones SL, Lohman B (October 2002). "Interactions between malaria and HIV infection-an emerging public health problem?". Microbes Infect. 4 (12): 1265–70. doi:10.1016/S1286-4579(02)01655-6. PMID 12467769.
- ^Abu-Raddad LJ, Patnaik P, Kublin JG (December 2006). "Dual infection with HIV and malaria fuels the spread of both diseases in sub-Saharan Africa". Science. 314 (5805): 1603–6. doi:10.1126/science.1132338. PMID 17158329.
- ^Bentwich Z, Kalinkovich A, Weisman Z (April 1995). "Immune activation is a dominant factor in the pathogenesis of African AIDS". Immunol. Today. 16 (4): 187–91. doi:10.1016/0167-5699(95)80119-7. PMID 7734046.
- ^Borkow G, Bentwich Z (May 2002). "Host background immunity and human immunodeficiency virus protective vaccines, a major consideration for vaccine efficacy in Africa and in developing countries". Clin. Diagn. Lab. Immunol. 9 (3): 505–7. doi:10.1128/CDLI.9.3.505-507.2002. PMC 119996. PMID 11986252.
- ^ abcSchistosomiasis. World Health Organization (WHO). 2004.[permanent dead link] Retrieved March 2011.
- ^ abScrimshaw NS, SanGiovanni JP (August 1997). "Synergism of nutrition, infection, and immunity: an overview". Am. J. Clin. Nutr. 66 (2): 464S–477S. PMID 9250134.
- ^Stephenson L (1993). "The impact of schistosomiasis on human nutrition". Parasitology. 107 (Suppl): S107–23. doi:10.1017/S0031182000075545. PMID 8115176.
- ^Harms G, Feldmeier H (June 2002). "HIV infection and tropical parasitic diseases — deleterious interactions in both directions?". Trop. Med. Int. Health. 7 (6): 479–88. doi:10.1046/j.1365-3156.2002.00893.x. PMID 12031069.
In this weekly series, Life's Little Mysteries provides expert answers to challenging questions.
Imagine a world with no HIV, no malaria, no tuberculosis, no flu and so on down to the absence of the common cold. With scientists chasing after cure-all anti-virus treatments and a universal flu vaccine in labs around the world, the eradication of infectious diseases certainly appears to be medical research's ultimate (if remote) goal. But what if we actually got there?
As the Princeton mathematical epidemiologist Nim Arinaminpathy put it, "If we had a magic pill that got rid of all infectious diseases, period, would we really use it?" He isn't sure. In all likelihood, purging humanity of infectious disease would not be a universally positive eventuality, but it wouldn't trigger the immediate downfall of Homo sapiens, either.
Survival of the unfittest
First, consider what we'd be giving up. "Our evolutionary history has been a continual arms race against the pathogens that plague us," said Vincent Racaniello, professor of microbiology and immunology at Columbia University. For eons, this battle has weeded out the weak, and in a less combative environment, standards for human survival would grow lax.
However, this is not quite as problematic as it might seem. In much of the West, "people are already kind of artificial animals," Racaniello told Life's Little Mysteries. "We have all these ways of intervening when people get sick, when otherwise they would have died and we would see some natural selection for people with more robust immune systems." But as long as doctors keep having a way to render moot those diseases that used to kill us, natural immunity isn't essential, he said.
And in fact, many diseases could be eradicated worldwide without any loss of evolutionary robustness. "With influenza, there isn't any indication that this plays a role in human evolution," said Arinaminpathy, who studies the evolutionary effects of flu vaccines. A pathogen can only impact human DNA if it tends to kill people before they have offspring. Otherwise, its victims have already passed on their genes to the next generation, regardless of whether those genes made them susceptible to the pathogen or not. The flu is most fatal to the elderly, who have typically already passed on their genes. [How Many Genetic Mutations Do I Have?]
Meanwhile, malaria does target the young, and it therefore molds the evolution of people in many tropical countries by killing children with feeble immune defenses (leaving behind those with malaria-resistant genes). But this "survival of the fittest" situation is not desirable; malaria has been largely eradicated in the United States with no obvious downsides. If the same were to happen in Africa and other afflicted regions, "the impact of reducing or removing malaria would go beyond public health," Arinaminpathy said.
A healthy population
The malaria parasite is so rampant in Africa that many children are afflicted over and over in a nearly continuous cycle. "You can't think clearly, you feel terrible, and it stops you from being able to go to school or have a productive life," Racaniello said. Meanwhile, HIV is running amok in sub-Saharan Africa, similarly stifling development and productivity. ['Superdrug' Could Fight Both HIV and Malaria]
In short, disease ushers in poverty. "If you get rid of infectious diseases by vaccination," Racaniello said, "you can make a big contribution to getting people out of poverty so they can have productive lives."
And although wiping out malaria, tuberculosis, sleeping sickness, HIV and the other tropical plagues would mean significant population growth in just the areas that are already experiencing runaway birth rates and food crises, these socioeconomic problems would be far more tractable in a disease-free society. "If a good fraction of these individuals have productive careers they might come up with solutions," he said.
These considerations all suggest eradicating infectious diseases would benefit humanity, on balance. But there's one giant question left.
Does regularly getting the cold or the flu when we're young help us later? These viruses might somehow aid in the growth and development of our metabolisms, or even our organs. Scientists aren't sure, because they haven't had the chance to study a virus-free human population, as they have with the bacteria- and parasite-lacking populations in the West.
"We're just learning that the consequence of antibiotics is that when you get rid of the good bacteria in our guts, we can develop autoimmune diseases [such as allergies]. We're not as advanced in our understanding of viruses. What do viruses do for us?" Racaniello said.
Allergies we can live with, but some of the benign viruses that hitch a ride in our bodies could be serving a much deeper role, Arinaminpathy said — as could a few of the slightly virulent ones with whom our relationship is "a bit fuzzy." Would a world in which babies were permanently inoculated against the cold, the flu, HPV and everything else actually be better?
Like always, we should we careful what we wish for. Ridding the world of diseases would be "mostly a good thing," Arinaminpathy said, "but there are these interesting questions when you scratch the surface of these illnesses."
This story was provided by Life's Little Mysteries, a sister site to LiveScience. Follow Natalie Wolchover on Twitter @nattyover. Follow Life's Little Mysteries on Twitter @llmysteries. We're also on Facebook & Google+.