A note on this page's publication date
The content we created in 2009 appears below. This content is likely to be no longer fully accurate, both with respect to the research it presents and with respect to what it implies about our views and positions.
Here we provide a basic discussion of developing-world diseases, in particular what their symptoms are (and to the extent we have information available) how common different symptoms are. We focus on diseases addressed by the charities we've covered and/or our priority programs.
Unless otherwise noted, all statistics on this page come from the World Health Organization's Global Burden of Disease Project files. These are available online on the project's statistics page [since this page was written, the WHO statistics page has been removed from it's previous URL].
- Vaccine-preventable diseases
- Neglected tropical diseases
HIV is a virus that is transmitted through sexual intercourse, contact with contaminated blood, or between a mother and child during birth or breastfeeding.1 The virus weakens an individual's immune system,2 making him or her susceptible to life-threatening diseases such as tuberculosis.3 UNAIDS estimates that the median time from HIV infection until death, without treatment, is 9-11 years.4 A review of eight developing-world studies estimated the median time from AIDS diagnosis to death as 6-19 months.5
Tuberculosis (TB) is an infection that is contracted when individuals inhale airborne droplets (produced when infected individuals cough, sneeze, or even talk).6 All else equal, approximately 5% of those infected with TB develop the progressive form of the disease within five years of infection.7 According to the Disease Control Priorities (DCP) report,
Malaria causes short-term illness and may cause death.12 Less frequently, it can cause permanent disability.13 It can also contribute to other problems such as anemia, low birthweight for babies of infected women, and growth retardation.14 It is often pointed to as a major economic burden.15
The table below summarizes malaria's largest consequences; note that the bottom two rows indicate an average of over 4 days sick per year for children under 5.19
|Type of impact||Age: 0 to 4||Age: 5 to 14||Age: 15+|
|Mortality per episode||.7%||.3%||.6%|
|Days sick per episode||5.1||2.3||2.7|
|Annual episodes per person||.89||.38||.07|
Diarrhea in young children living in poverty can be so severe that it results in death by dehydration. It primarily affects children under five years old.20 In sub-Saharan Africa, a child under 5 has, on average, over 3 episodes per year of diarrhea;21 in 2001, about 1.8 million children living in low- and middle-income countries died from diarrhea.22
The bacteria responsible for many of these cases of lethal diarrhea are found in human feces and can reach a person in many possible ways, including a contaminated water supply (speaking informally, most water-related projects we've seen focus on diarrhea prevention as their justification).23 However, there are also many other ways to contract diarrhea, and thus many other ways to reduce the number of deaths from this disease. More at our discussion of water charities.
Pneumonia is a respiratory infection, and is, according to the World Health Organization, the leading cause of death of children under the age of five globally.24 Pneumonia is an infectious disease and can be spread through bacteria, viruses, or fungi.25 Pneumonia causes difficult breathing, fever, and cough.26
In developing countries, the case-fatality rate in children with viral pneumonia ranges from 1.0 to 7.3 percent. For bacterial pneumonia this rate is 10 to 14 percent and for mixed viral and bacterial infections it is 16 to 18 percent.27 The World Health Organization (WHO) estimates that 1.8 million children under five die of pneumonia each year.28
Poliomyelitis (polio) is a highly infectious disease, which mainly affects children under the age of 5.29 The virus is transmitted through contaminated food and water.30 Initial symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs.31 In a small proportion of cases, the disease causes paralysis, which affects approximately 1 of every 200 individuals infected. Among those paralyzed, 5% to 10% die when their muscles become immobilized.32 The World Health Organization currently estimates a low rate of incidence: about 2000 reported cases in 2006. In 2008, only four countries in the world were polio-endemic: Afghanistan, India, Nigeria and Pakistan.33
Diphtheria is spread through close physical contact, mainly through droplets produced from coughing and sneezing.34 Symptoms range from a sore throat to life-threatening respiratory infection. Diphtheria can also cause toxic damage to heart muscles and/or peripheral nerves.35
The World Health Organization estimates between 5% and 10% of diphtheria patients die, even if properly treated.36 In countries still burdened with diphtheria, young children are most commonly affected. In industrialized countries, endemic diphtheria is extremely rare.37
The measles virus is a highly contagious disease transmitted by respiratory droplets. Symptoms include high fever, runny nose, bloodshot eyes, white spots on the inside of the mouth, and rash.38 "Patients normally improve by the third day of rash, and are fully recovered 7–10 days from the onset of disease."39 More serious cases come about by measles complications such as malnutrition and permanent neurological disorders.40 Blindness, encephalitis, diarrhea, ear infection and pneumonia may also occur.41
"In most industrialized nations, measles is well controlled or even eliminated."42 Measles continues to be a leading cause of death among young children, especially in Africa and south and east Asia.43 Case fatality rates are 5-15% in developing countries and .01%-.1% in developed countries.44
Hepatitis B, also known as HBV, is highly contagious and is transmitted by exposure to infected blood and other body fluids (i.e. semen and vaginal fluid).45 "Common modes of transmission include mother-to-infant, child-to-child, unsafe injection practices, blood transfusions and sexual contact."46 The virus, which attacks the victim's liver, can cause symptoms that last several weeks, including "yellowing of the skin and eyes (jaundice), dark urine, extreme fatigue, nausea, vomiting and abdominal pain."47 HBV can also cause a chronic liver infection that can later develop into cirrhosis of the liver or liver cancer.48
"High prevalence of chronic HBV infection is found in areas of sub-Saharan Africa, South-East Asia, the Eastern Mediterranean countries, south and western Pacific islands, the interior of the Amazon basin and in certain parts of the Caribbean."49 The World Health Organization's position paper on Hepatitis B examines differences in contraction and mortality rates as determined by the mode of transmission and age:50
- Acute hepatitis B occurs in about: 1% of perinatal, 10% of childhood, and 30% of late (>5 years) HBV infections.
- .1-.6% of acute cases turn into "fulminant cases" (characterized by a breakdown in liver function; 70% of fulminant cases are fatal). This breaks down to mortality rates from HBV of: .0007%-.0042% of infants, .007%-.042% of children, and .021%-.126% of infected adults.
- The development of chronic HBV infection is inversely related to age and occurs in approximately 90% of persons infected perinatally, in 30% infected in early childhood and in 6% infected after 5 years of age. Persons with chronic HBV infection have a 15–25% risk of dying prematurely from HBV-related cirrhosis and HCC.
Yellow fever is a virus spread by infected mosquitoes.51 Following infection from a bite, a three to six day incubation period occurs before symptoms appear.52 Symptoms include intense headache, fever, chills, and myalgia.53 Serious cases occur in 15% of cases, causing symptoms such as jaundice, liver and kidney failure and cardiovascular collapse. About 20-50% of patients with liver or kidney failure die, in most cases 7-10 days after onset of disease.54 Survivors usually experience complete recovery of the liver and kidneys.55
Once a worldwide disease, yellow fever mainly persists in West and Central Africa, the northern half of South America, and Panama. "WHO estimates that a total of 200,000 cases of yellow fever occur each year, with about 30,000 deaths. More than 90% of yellow fever cases occur in Africa, where over 500 million people live in the yellow fever at-risk zone between 15Â° north and 15Â° south of the equator."56
Haemophilus influenzae Type b (Hib)
"Hib is transmitted through the respiratory tract and causes meningitis, pneumonia, septic arthritis, skin infections, epiglottitis, osteomyelitis, and sepsis. Deaths caused by Hib occur primarily from meningitis and pneumonia."57
"The disease burden is highest among those aged between 4 months and 18 months, but the Hib disease is occasionally observed in infants younger than 3 months and among those older than 5 years. In unvaccinated populations, Hib is the dominant cause of non-epidemic bacterial meningitis during the first year of life. Even with prompt and adequate antibiotic treatment, 3-20% of patients with Hib meningitis die."58
Hib has been almost completely eliminated in the industrialized world and has been dramatically reduced in some parts of the developing world.59
Pertussis, also known as "whopping cough," is transmitted through close respiratory contact. After a 7-10 day incubation period, patients develop coughing symptoms from the bacterium.60 Recovery depends on the age and immunization status of the patient. Serious symptoms and death are reported mainly in non-immune young infants. Complications occur in 5-6% of cases, most frequently in infants under six months. In developing countries, case fatality for infants is about 4%.61 "Most pertussis occurs in school-aged children in developing countries."62
Tetanus is transmitted through spores that enter the body through wounds or the umbilical cord stump.63 The majority of cases are associated with childbirth and occur through unclean deliveries and poor post-natal hygiene, mainly in the developing world.64 Symptoms of tetanus include spasms of facial muscles, back muscles, and the throat, which may cause sudden death. Seizures may also occur. The overall case-fatality rate varies between 10% and 70%, depending on treatment, age, and general health of patient.65
Neglected tropical diseases
"Neglected tropical diseases" are a specific set of chronic infectious diseases found primarily in tropical areas, and do not include such well-known diseases as AIDS, tuberculosis and malaria.66
There are three prominent types of soil-transmitted helminths (STHs), or intestinal worms: trichuriasis (or whipworm), hookworm, and ascariasis (or roundworm). Each affects the following number of people worldwide:67
- Trichuriasis: 26 million people
- Hookworm: 60 million people
- Ascariasis: 58 million people
They cause a variety of chronic symptoms:68
- Chronic pain
STHs may also severely impair mental and physical growth in children.69 Hookworm in pregnant women causes premature births, low birth-weight, and impaired lactation.70 We have not found data regarding the prevalence of symptoms for those infected, nor have we found any detailing the distribution of symptom severity.
Schistosomiasis is caused by parasites, and is passed through infested water.71 "Many people infected remain asymptomatic; about 80% of infected children show early symptoms."72 Specific symptoms depend on several factors including the type and progression of schistosomiasis, and can include:
- Hematuria (blood in the urine) or dysuria (painful urination) early in the disease's progression.73
- Urinary tract infections and other bladder problems at later stages, potentially leading to bladder cancer and kidney failure.74
- Bloody diarrhea, bloody stools, abdominal pain, and liver failure.75
- Anemia, malnutrition, and impaired growth and cognitive function in children with repeated infections.76
- Death. There is large disagreement about the number of annual fatalities due to schistosomiasis-caused non-functioning kidneys and hematemesis (estimates range from under 27,000 to 280,000).77
- Hydrocele: swollen scrotum
- Lymphedema: enlargement and swelling of the limbs
- Elephantiasis: extreme swelling of limbs, scrotum or breasts
These symptoms can cause suffering beyond the direct physical manifestations, leaving people bedridden for days, and those infected may suffer from societal discrimination that impairs their professional and personal life.81
Lymphatic filariasis primarily causes disability (as opposed to mortality):82
- Approximately 65 million people worldwide have symptoms due to lymphatic filariasis. Many others are asymptomatic.
- Lymphatic filariasis causes approximately 300 deaths each year.
Onchocerciasis (aka river blindness)
Onchocerciasis is caused by a worm that is passed to humans by blackflies. These flies tend to breed near streams.83 The disease can ultimately result in low vision, blindness and/or severe skin disease associated with extreme itching.84
Onchocerciasis is most common in Central and West Africa (90% of cases), but also occurs Latin America and parts of the Arabian Peninsula.85
Trachoma is most commonly transmitted by flies.86
Repeated infections with trachoma cause eyelids to turn in and cause contact between eyelashes and the surface of the eye, which leads to low vision and, eventually, blindness.87
Dracunculiasis (aka guinea worm)
Guinea worm is transmitted when a person drinks contaminated water.88 A worm is passed through the water and grows inside the person until it eventually emerges in a "long and painful process that can last 8 to 12 weeks."89 The burning pain caused during this process often leads people to submerge in water, which causes the blister to rupture and contaminate the water, aiding transmission.90
Guinea worm is rarely fatal, but it causes severe pain and debilitation, often leaving those infected bedridden for more than a month.91 "The disease's other symptoms, including nausea, vomiting, diarrhea, and dizziness, further exacerbate this burden. Secondary bacterial infections occur in about half of all cases and can lead to arthritis, 'locked' joints, tetanus, and permanent crippling."92
- Addiss, David, et al. 2005. Albendazole for lymphatic filariasis. Cochrane Database of Systematic Reviews 2005, Issue 4. Summary available at http://www.cochrane.org/reviews/en/ab003753.html (accessed April 23, 2010). Archived by WebCite® at http://www.webcitation.org/5pCl8FC8Q.
- Danso-Appiah, A., et al. 2008. Drugs for treating urinary schistosomiasis. Cochrane Database of Systematic Reviews 2008, Issue 3. Summary available at http://www.cochrane.org/reviews/en/ab000053.html (accessed April 26, 2010). Archived by WebCite® at http://www.webcitation.org/5pHThGp7G.
- GiveWell. Malaria statistics (XLS).
- Jamison, Dean T., et al., eds. 2006. Disease control priorities in developing countries (PDF). 2nd ed. New York: Oxford University Press.
- Levine, Ruth. 2007. Case 11: Reducing guinea worm in Asia and sub-Saharan Africa (PDF). In Case studies in global health: Millions saved. Sudbury, MA: Jones and Bartlett.
- Lengeler, C. 2004. Insecticide-treated bed nets and curtains for preventing malaria. Cochrane Database of Systematic Reviews 2004, Issue 2. Summary available at http://www.cochrane.org/reviews/en/ab000363.html (accessed April 19, 2010). Archived by WebCite® at http://www.webcitation.org/5p6S58mQu.
- Lopez, Alan D., et al., eds. 2006. Global burden of disease and risk factors (PDF). New York: Oxford University Press.
- Mathers, Colin D., Majid Ezzati, and Alan D. Lopez. 2007. Measuring the burden of neglected tropical diseases: The global burden of disease framework (PDF). PLoS Neglected Tropical Diseases 1, no. 2.
- Public Library of Science Neglected Tropical Diseases. Journal Scope. http://www.plosntds.org/static/scope.action (accessed May 3, 2010). Archived by WebCite® at http://www.webcitation.org/5pSP5DBhK.
- Sachs, Jeffrey D., and John Luke Gallup. 2001. The Economic Burden of Malaria (PDF). Am. J. Trop. Med. Hyg. 64: 85-96.
- Saconato, Humberto, and Ãlvaro N. Atallah. 1999. Interventions for treating schistosomiasis mansoni. Cochrane Database of Systematic Reviews 1999, Issue 3. Summary available at http://www.cochrane.org/reviews/en/ab000528.html (accessed April 26, 2010). Archived by WebCite® at http://www.webcitation.org/5pHTwwC6J.
- UNAIDS Reference Group on Estimates, Modelling, and Projections. 2006. Improving parameter estimation, projection methods, uncertainty estimation, and epidemic classification (PDF).
- World Health Organization. Diarrhoeal disease. http://www.who.int/mediacentre/factsheets/fs330/en/index.html (accessed May 7, 2010). Archived by WebCite® at http://www.webcitation.org/5pY8ZDLpB.
- World Health Organization. Diphtheria. http://www.who.int/mediacentre/factsheets/fs089/en/ (accessed May 7, 2010). Archived by WebCite® at http://www.webcitation.org/5pYFrQROa.
- World Health Organization. Disease and injury regional estimates for 2004: Deaths for WHO regions (XLS).
- World Health Organization. Disease and injury regional estimates for 2004: Prevalence for WHO regions (XLS).
- World Health Organization. Hepatitis B. http://www.who.int/mediacentre/factsheets/fs204/en/ (accessed May 3, 2010). Archived by WebCite® at
- World Health Organization. HIV/AIDS. http://www.who.int/features/qa/71/en/index.html (accessed May 6, 2010). Archived by WebCite® at http://www.webcitation.org/5pWf6IrwE.
- World Health Organization. Lives at risk: Malaria in pregnancy. http://www.who.int/features/2003/04b/en/ (accessed June 10, 2010). Archived by WebCite® at http://www.webcitation.org/5qNt4NOPX.
- World Health Organization. Lymphatic Filariasis. http://www.who.int/mediacentre/factsheets/fs102/en/index.html (accessed May 3, 2010). Archived by WebCite® at http://www.webcitation.org/5pCmimYsV.
- World Health Organization. Onchocerciasis (river blindness) - Disease Information. http://www.who.int/blindness/partnerships/onchocerciasis_disease_informa... (accessed May 3, 2010). Archived by WebCite® at http://www.webcitation.org/5pSQOifbD.
- World Health Organization. Pneumonia. http://www.who.int/mediacentre/factsheets/fs331/en/index.html (accessed May 7, 2010). Archived by WebCite® at http://www.webcitation.org/5pYALVWE8.
- World Health Organization. Poliomyelitis. http://www.who.int/topics/poliomyelitis/en/ (accessed May 7, 2010). Archived by WebCite® at http://www.webcitation.org/5pYDOIAk2.
- World Health Organization. Poliomyelitis fact sheet. http://www.who.int/mediacentre/factsheets/fs114/en/index.html (accessed May 7, 2010). Archived by WebCite® at http://www.webcitation.org/5pYDK71EC.
- World Health Organization. Priority eye diseases: Trachoma. http://www.who.int/blindness/causes/priority/en/index2.html (accessed May 3, 2010). Archived by WebCite® at http://www.webcitation.org/5pHhol7m2.
- World Health Organization. Schistosomiasis. http://www.who.int/mediacentre/factsheets/fs115/en/index.html (accessed April 26, 2010). Archived by WebCite® at http://www.webcitation.org/5pHUQjziH.
- World Health Organization. Weekly epidemiological record (October 3, 2003) (PDF).
- World Health Organization. Weekly epidemiological record (April 2, 2004) (PDF).
- World Health Organization. Weekly epidemiological record (July 9, 2004) (PDF).
- World Health Organization. Weekly epidemiological record (January 28, 2005) (PDF).
- World Health Organization. Weekly epidemiological record (January 20, 2006) (PDF).
- World Health Organization. Weekly epidemiological record (May 19, 2006) (PDF).
- World Health Organization. Weekly epidemiological record (November 24, 2006) (PDF).
- World Health Organization. Yellow Fever: Background. http://www.who.int/biologicals/areas/vaccines/yellow_fever/yellow_fever_... (accessed May 3, 2010). Archived by WebCite® at http://www.webcitation.org/5pSOPe8nq.
- Yorston, David, et al. 2006. Interventions for trachoma trichiasis. Cochrane Database of Systematic Reviews 2006, Issue 3. Summary available at http://www.cochrane.org/reviews/en/ab004008.html (accessed April 26, 2010). Archived by WebCite® at http://www.webcitation.org/5pHhuBUj8.
- Zwahlen, Marcel, and Matthias Egger. 2006. Progression and mortality of untreated HIV-positive individuals living in resource-limited settings: Update of literature review and evidence synthesis (PDF). Switzerland: UNAIDS.
"HIV is transmitted through unprotected sexual intercourse (anal or vaginal), transfusion of contaminated blood, sharing of contaminated needles, and between a mother and her infant during pregnancy, childbirth and breastfeeding." World Health Organization, "HIV/AIDS."
"The human immunodeficiency virus (HIV) is a retrovirus that infects cells of the human immune system, destroying or impairing their function. In the early stages of infection, the person has no symptoms. However, as the infection progresses, the immune system becomes weaker, and the person becomes more susceptible to so-called opportunistic infections." World Health Organization, "HIV/AIDS."
"What is the most common life-threatening opportunistic infection affecting people living with HIV/AIDS? Tuberculosis (TB) kills nearly a quarter of a million people living with HIV each year. It is the number one cause of death among HIV-infected people in Africa, and a leading cause of death in this population worldwide." World Health Organization, "HIV/AIDS."
"The Reference Group recommended that median survival of HIV+ individuals should be increased to 11.5 years for females and 10.5 years for males for all countries with generalised epidemics. For Thailand, where subtype E dominates, the default median life expectancy should remain 9 years. These recommendations should be reviewed in the light of new evidence as it becomes available." UNAIDS Reference Group on Estimates, Modelling, and Projections 2006, Pg 7-8.
"Eight studies from resource-limited settings provided data on the time between the occurrence of first AIDS-defining events and death. Median survival after diagnosis of AIDS ranged between 6 and 19 months." Zwahlen and Egger 2006, Pg 5.
"Human TB is caused by infection with mycobacteria, principally Mycobacterium tuberculosis. Individuals with pulmonary or laryngeal TB produce airborne droplets while coughing, sneezing, or simply talking. Inhaled infectious droplets lodge in the alveoli, and bacilli are taken up there by macrophages, beginning a series of events that results in either the containment of infection or the progression to active disease (Frieden and others 2003). Following uptake by macrophages, M. tuberculosis replicates slowly but continuously and spreads through the lymphatic system to hilar lymph nodes. In most infected people, cell-mediated immunity, associated with a positive tuberculin test, develops two to eight weeks after infection. Activated T lymphocytes and macrophages form granulomas, which limit the further replication and spread of bacilli. Unless a later defect occurs in cell-mediated immunity, the infection remains contained within the granulomas." Jamison et al. 2006, Pg 290.
"When the immune response cannot suppress replication, primary infection leads to active TB (progressive primary TB).In the absence of other predisposing conditions, only about 5 percent of infected people develop progressive pri- mary disease within five years of infection (Comstock, Livesay, and Woolpert 1974; Sutherland 1968, 1976). After five years, the annual risk of developing TB by the reactivation of latent infection is much lower (â‰ˆ10^4 per capita per year)." Jamison et al. 2006, Pg 290.
"The most common clinical manifestation is pulmonary disease, typically in the parenchyma of the middle and lower lung. In the most infectious patients, bacilli can be seen micro- scopically on stained sputum smears (60 to 70 percent of pulmonary cases; Marais and others 2004; Styblo 1991). Smear-negative patients may also be infectious but, per patient, contribute relatively little to transmission (Behr and others 1999; Hernandez-Garduno and others 2004)." Jamison et al. 2006, Pg 290.
Jamison et al. 2006, Pg 291.
"In Africa, malaria accounts for an estimated 25% of all childhood mortality below age five, excluding neonatal mortality (WHO 2003)." Lengeler 2004, Pg 3.
"Human infection begins when the malaria vector, a female anopheline mosquito, inoculates plasmodial sporozoites from its salivary gland into humans during a blood meal. The sporozoites mature in the liver and are released into the bloodstream as merozoites. These invade red blood cells, causing malaria fevers. Some forms of the parasites (gametocytes) are ingested by anopheline mosquitoes during feeding and develop into sporozoites, restarting the cycle." Jamison et al. 2006, Pg 413.
"More than 3 billion people live in malarious areas and the disease causes between 1 million and 3 million deaths each year (Breman, Alilio, and Mills 2004; Snow and others 2003)." Jamison et al. 2006, Pg 413.
See Jamison et al. 2006, Pg 416, Table 21.3. For estimates of cases of hearing impairment, visual impairment, epilepsy, etc. caused by malaria.
"The DALY model of malaria does not sufficiently take it into account as an indirect cause of broader morbid risks. Some consider anemia to be caused indirectly unless linked to acute, high-density parasitemia. Similarly, low birthweight may also be indirectly attributable to malaria, and a child's later undernutrition and growth retardation linked to malaria infection enhances the severity of other concomitant or comorbid infectious diseases through immune suppression. Thus, malaria infection contributes to broad causes of mortality beyond the direct fatal consequences of infection and is probably underestimated (Breman, Alilio, and Mills 2004; Snow and others 2003). In Africa, pregnant women experience few malaria-specific fever episodes but have an increased risk of anemia and placental sequestration of the parasite. Maternal clinical manifestations are more apparent in areas with less intense transmission, particularly in Asia. Estimates indicate that in Sub-Saharan Africa, malaria-associated anemia is responsible for 3.7 percent of maternal mortality, or approximately 5,300 maternal deaths annually. Prematurity and intrauterine growth retardation resulting in low birthweight associated with maternal malaria account for 3 to 8 percent of infant mortality in Africa (Steketee and others 1996, 2001)." Jamison et al. 2006, Pg 417.
Sachs and Gallup 2000.
Jamison et al. 2006, Pg 415, Table 21.1.
Jamison et al. 2006, Pg 416, Table 21.3.
"Pregnant women are particularly vulnerable to malaria as pregnancy reduces a woman's immunity to malaria, making her more susceptible to malaria infection and increasing the risk of illness, severe anaemia and death." World Health Organization, "Lives at Risk: Malaria in Pregnancy."
Number of episodes, days of illness, and malaria mortality are from Jamison et al. 2006, Pg 416. Population for Africa is from World Health Organization, "Disease and injury regional estimates for 2004: Deaths for WHO regions." Calculations are in GiveWell, "Malaria Statistics."
"Diarrhoeal disease is the second leading cause of death in children under five years old, and is responsible for killing 1.5 million children every year. Diarrhoea can last several days, and can leave the body without the water and salts that are necessary for survival. Most people who die from diarrhoea actually die from severe dehydration and fluid loss." World Health Organization, "Diarrhoeal Disease."
"Remarkably, the estimated median incidence of diarrheal disease in children under five in developing countries has not changed much since the early 1990s (figure 19.1): 3.2 episodes per child per year in 2003 (Parashar and others 2003) compared with 3.5 episodes per child per year in 1993 (Jamison and others 1993)." Jamison et al. 2006, Pg 373.
Lopez et al. 2006, Pg 126, Table 3B.1.
"Diarrhoea is a symptom of infections caused by a host of bacterial, viral and parasitic organisms, most of which are spread by faeces-contaminated water...Diarrhoeal disease can also spread from person-to-person, aggravated by poor personal hygiene. Food is another major cause of diarrhoea when it is prepared or stored in unhygienic conditions. Water can contaminate food during irrigation. Fish and seafood from polluted water may also contribute to the disease." World Health Organization, "Diarrhoeal Disease."
"Pneumonia is a form of acute respiratory infection that affects the lungs. The lungs are made up of small sacs called alveoli, which fill with air when a healthy person breathes. When an individual has pneumonia, the alveoli are filled with pus and fluid, which makes breathing painful and limits oxygen intake. Pneumonia is the single largest cause of death in children worldwide. Every year, it kills an estimated 1.8 million children under the age of five years, accounting for 20% of all deaths of children under five years old worldwide." World Health Organization, "Pneumonia."
"Pneumonia is caused by a number of infectious agents, including viruses, bacteria and fungi." World Health Organization, "Pneumonia."
"The symptoms of pneumonia include:
- rapid or difficult breathing
- loss of appetite
- wheezing (more common in viral infections).
When pneumonia becomes severe, children may experience lower chest wall indrawing, where their chests move in or retract during inhalation (in a healthy person, the chest expands during inhalation). Infants may be unable to feed or drink and may also experience unconsciousness, hypothermia and convulsions." World Health Organization, "Pneumonia."
"In developing countries, the case-fatality rate in children with viral pneumonia ranges from 1.0 to 7.3 percent (John and others 1991; Stensballe, Devasundaram, and Simoes 2003), with bacterial pneumonia from 10 to 14 percent and with mixed viral and bacterial infections from 16 to 18 percent, much higher than the 5 to 10 percent for children not infected with HIV (Bobat and others 1999; Madhi, Petersen, Madhi, Khoosal,and others 2000; Nathoo and others 1993; Zwi, Pettifior, and Soderlund 1999)." Jamison et al. 2006, Pg 485.
"Pneumonia kills an estimated 1.8 million children every year – more than AIDS, malaria and measles combined." World Health Organization, "Pneumonia."
"Polio is a highly infectious disease caused by a virus...Polio mainly affects children under five years of age." World Health Organization, "Poliomyelitis fact sheet."
"The virus is transmitted through contaminated food and water, and multiplies in the intestine, from where it can invade the nervous system." World Health Organization, "Poliomyelitis."
"Initial symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs." World Health Organization, "Poliomyelitis."
"One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, 5% to 10% die when their breathing muscles become immobilized." World Health Organization, "Poliomyelitis fact sheet."
World Health Organization, "Poliomyelitis fact sheet."
"Diphtheria is an infectious disease spreading from person to person by respiratory droplets from the throat through coughing and sneezing." World Health Organization, "Diphtheria."
"Symptoms range from a moderately sore throat to toxic life-threatening diphtheria of the larynx or of the lower and upper respiratory tracts. Diphtheria is often complicated by diphtheric myocarditis (toxic damage to heart muscles) and neuritis (toxic damage to peripheral nerves)." World Health Organization, "Diphtheria."
World Health Organization, "Diphtheria."
"In countries where diphtheria is still endemic, preschool and school-age children are most commonly affected. In most industrialized countries, endemic diphtheria has disappeared or become extremely rare." World Health Organization, "Weekly Epidemiological Record (January 20, 2006)," Pg 26.
"The virus is an exclusive human pathogen–it has no animal reservoir and no vector. It is transmitted by respiratory droplets, via aerosol and direct contact...Some 5–7 days after exposure, the infection is spread through the bloodstream to the skin, and conjunctivae and within the respiratory tract. Viraemia peaks towards the end of the incubation period, when patients develop prodromal symptoms of high fever, cough, coryza and conjunctivitis. The typical rash appears after another 3–4 days, often accompanied by fever peaking at 39–40 Â°C. The maculo-papular rash spreads from the face and neck to the trunk and extremities, fading after about 3 days. At the onset of rash, bluish-white Koplik's spots, which are pathognomonic of measles, may be seen in the oral mucosa." World Health Organization, "Weekly epidemiological record (April 2, 2004)," Pg 132.
World Health Organization "Weekly epidemiological record (July 9, 2004)," Pg 113.
"Many more individuals suffer from measles complications such as severe malnutrition (including aggravated vitamin A deficiency), deafness, blind- ness or damage to the central nervous system." World Health Organization "Weekly epidemiological record (July 9, 2004)," Pg 113.
"More than 90 percent of infections are associated with clinical disease (Krugman 1963). Complications include pneumonia, diarrhea, encephalitis, and blindness, especially in children with vitamin A deficiency." Jamison et al. 2006, Pg 395.
World Health Organization, "Weekly epidemiological record (July 9, 2004)," Pg 130.
"However, despite about 70% global vaccination coverage, measles remains the leading vaccine-preventable killer of children. In 2002, the number of global measles deaths was estimated to be approximately 610,000, with most deaths occurring among infants and young children living in Africa and south and east Asia." World Health Organization, "Weekly epidemiological record (July 9, 2004)," Pg 132.
"In developing countries, investigations have generally found case–fatality rates to be in the range 5–15%. In devel- oped countries, measles deaths are rare, with case-fatality ratios in the range of 0.01–0.1%." World Health Organization, "Weekly epidemiological record (July 9, 2004)," Pg 134.
"Humans are the only reservoir of HBV. The virus is highly contagious and is transmitted by percutaneous and per- mucosal exposure to infected blood and other body fluids (i.e. semen and vaginal fluid)." World Health Organization,"Weekly epidemiological record (July 4, 2004)," Pg 257.
World Health Organization,"Weekly epidemiological record (July 4, 2004)," Pg 257.
World Health Organization, "Hepatitis B."
"It can cause chronic liver disease and puts people at high risk of death from cirrhosis of the liver and liver cancer." World Health Organization, "Hepatitis B."
World Health Organization, "Weekly epidemiological record (April 2, 2004)," Pg 257.
World Health Organization, "Weekly epidemiological record (April 2, 2004)."
"Exposure of susceptible persons to bites from infected mosquitoes is the only significant mode of YF transmission." World Health Organization, "Yellow Fever: Background."
"Yellow fever virus is transmitted by mosquitoes, primarily Aedes eqypti, with a three-to six-day incubation period." Jamison et al. 2006, Pg 396.
"Patients present with intense headache, fever, chills, and myalgia, among other symptoms." Jamison et al. 2006, Pg 396.
"However, in approximately 15% of cases, the disease progresses, with or without a brief (24-48 hours) remission, to a more severe form, with fever, vomiting, epigastric pain, jaundiace, renal failure and haemorrhagic manifestations. The haemorrhagic manifestations are caused by reduced synthesis of clotting factors as well as by a comsumptive coagulopathy. Encephalitis due to YF virus is exceedingly rare. About 20-50% of patients with hepato-renal failure die, in most cases 7-10 days after onset of disease." World Health Organization, "Weekly epidemiological record (October 3, 2003)," Pg 353-354.
"Patients surviving YF may experi- ence prolonged weakness and fatigue, but healing of the liver and kidney injuries is usually complete." World Health Organization, "Weekly epidemiological record (October 3, 2003)," Pg 354.
World Health Organization, "Weekly epidemiological record (October 3, 2003)," Pg 351.
Jamison et al. 2006, Pg 396.
World Health Organization, "Weekly epidemiological record (November 24, 2006)," Pg 447.
"As a consequence, invasive Hib disease has been practically eliminated in many industrialized countries, and its incidence has been dramatically reduced in some parts of the developing world." World Health Organization, "Weekly epidemiological record (November 24, 2006)," Pg 446.
"B. pertussis is transmitted from infected to susceptible individuals through close respiratory contact. Following an incubation period of 7–10 days, patients develop catarrhal symptoms including cough. In the course of 1–2 weeks, coughing paroxysms ending in the classical whoop may occur." World Health Organization, "Weekly epidemiological record (January 28, 2005)," Pg 34.
"Complications occur in 5–6% of pertussis cases, most frequently in infants aged
The WHO estimated about 17.6 million cases of pertussis worldwide in 2003. 90% of those cases were in developing countries and 279,000 died from the disease.
World Health Organization, "Weekly epidemiological record (January 28, 2005)," Pg 32.
Jamison et al. 2006, Pg 394.
Jamison et al. 2006, Pg 390, Table 20.1.
"The disease remains an important public health problem in many parts of the world, particularly in the poorest districts of tropical developing countries, where tetanus morbidity and mortality are dominated by MNT [maternal and neonatal tetanus]...Maternal tetanus is a consequence of unclean delivery or abortion practices, and neonatal tetanus occurs when unclean instruments are used to cut the umbilical cord or when contaminated material is used to cover the umbilical stump in babies without protective concentrations of tetanus-specific antibody." World Health Organization, "Weekly epidemiological record (May 19, 2006)," Pg 200.
"Characteristic features are early spasms of the facial muscles (trismus or “lock-jaw” and “risus sardonicus”) followed by spasm of the back muscles (opisthotonos) and sudden, generalized tonic seizures (tetanospasms). Spasm of the glottis may cause sudden death. In neonatal tetanus, generalized spasms are commonly preceded by inability to suck or feed and excessive crying. The overall tetanus case-fatality rate varies between 10% and 70%, depending on treatment, age and general health of the patient." World Health Organization, "Weekly epidemiological record (May 19, 2006)," Pg 201.
Public Library of Science Neglected Tropical Diseases, "Journal Scope."
Mathers, Ezzati, and Lopez 2007, Pg 8.
"The Disease Control Priorities Project helminth working group has determined that the WHO global burden of disease estimates are low because they do not incorporate the full clinical spectrum of helminth-associated morbidity and chronic disability, including anemia, chronic pain, diarrhea, exercise intolerance, and undernutrition (King, Dickman, and Tisch 2005)." Jamison et al. 2006, Pg 471. We don't know whether these symptoms apply to both STHs and schistosomiasis or just one of them. Because of the lack of specificity in the sources we consulted, we would guess that the consensus is that both are a cause for all symptoms listed.
- "Chronic STH infections resulting from Ascaris, Trichuris, and hookworm can dramatically affect physical and mental development in children (WHO 2002)." Jamison et al. 2006, Pg 468.
- "In addition to their health effects, helminth infections also impair physical and mental growth in childhood, thwart educational advancement, and hinder economic development." Jamison et al. 2006, Pg 467.
"Because of their underlying poor iron status, children, women of reproductive age, and pregnant women are frequently the ones most susceptible to developing hookworm anemia (Brooker, Bethony, and Hotez 2004). Iron deficiency anemia during pregnancy has been linked to adverse maternal-fetal consequences, including prematurity, low birthweight, and impaired lactation (WHO 2002)." Jamison et al. 2006, Pg 468.
"People become infected when larval forms of the parasite – released by freshwater snails – penetrate their skin during contact with infested water.... There are two major forms of schistosomiasis – intestinal and urogenital – caused by five main species of blood fluke (see table)." World Health Organization, "Schistosomiasis."
Danso-Appiah et al. 2008, Pg 3.
"Haematuria (blood in urine) and dysuria (painful urination) are the main early symptoms of the disease." Danso-Appiah et al. 2008, Pg 3.
"Late-stage complications are insidious and include calcification of the bladder wall, bladder stones, and secondary bacterial infection (Jordan 1993). Tissue damage caused by trapped eggs can lead to diffuse or localized wall thickening of the bladder and the distal ureter hydronephrosis orhydroureter, which may eventually lead to kidney failure (Kardorff 2001; WHO 2002; van der Werf 2003). Elevated urine albumin levels and reported pain upon micturition by children have a strong correlation with S. haematobium infection (Rollinson 2005). An important long-term consequence of infection is squamous cell carcinoma of the bladder (Jordan 1993; King 2005; Shiff 2006). A recent review points out that bladder carcinoma is the seventhmost common cancer worldwide in men and that the highest incidence rate among men is found in Egypt (37.1 per 100,000 person-years) (Murta-Nascimento 2007), which might be related to S. haematobium infection and morbidity (Jordan 2000)." Danso-Appiah et al. 2008, Pg 3.
"Schistosomiasis infects the intestine, liver, and spleen. It can cause bloody diarrhoea, bloody stools, and abdominal pain (Gryseels 1992; WHO 1993). Infection of the liver and spleen causes liver fibrosis and portal hypertension that are generally irreversible in the late stages and kill patients, sometimes as a result of haemorrhage from varices (WHO 1993). Liver failure may also occur, especially when S. mansoni infection is associated with viral hepatitis (Pereira 1994)." Saconato and Atallah 1999, Pg 3.
"Sustained heavy infection leads to iron deficiency anaemia and other nutritional deficiencies, especially in children (Awasthi 2003; King 2005). The disease often results in retarded growth, reduced physical activity, and impaired cognitive function in children (Stephenson 1993; Nokes 1999; PCD 1999; Jukes 2002; WHO 2002)." Danso-Appiah et al. 2008, Pg 3.
"WHO (2002) estimates that 27,000 people die annually from STH infections and schistosomiasis (case fatality rate of 0.0014 percent). Many investigators, however, believe that this figure is an underestimate. Crompton (1999) estimated that 155,000 deaths annually occur from these infections (case fatality rate of 0.08 percent), whereas Van der Werf and others (2003), using the limited data available from Africa, estimated the schistosomiasis mortality alone at 280,000 per year (case fatality rate of 0.014 percent) because of nonfunctioning kidneys (from S. haematobium) and hematemesis (from S. mansoni). Therefore, the difference between estimates for helminth-associated mortality is more than 10-fold." Jamison et al. 2006, Pg 470.
"The thread-like, parasitic filarial worms Wuchereria bancrofti and Brugia malayi that cause lymphatic filariasis live almost exclusively in humans. These worms lodge in the lymphatic system, the network of nodes and vessels that maintain the delicate fluid balance between the tissues and blood and are an essential component for the body's immune defence system. They live for 4-6 years, producing millions of immature microfilariae (minute larvae) that circulate in the blood.... The disease is transmitted by mosquitoes that bite infected humans and pick up the microfilariae that develop, inside the mosquito, into the infective stage in a process that usually takes 7-21 days. The larvae then migrate to the mosquitoes' biting mouth-parts, ready to enter the punctured skin following the mosquito bite, thus completing the cycle. " World Health Organization, "Lymphatic Filariasis."
"Infected people can harbor microfilaremia without overt clinical manifestations." Jamison et al. 2006, Pg 434.
"Clinical symptoms and signs include hydrocoele (excess fluid inside the scrotal sac), lymphoedema (swelling and enlargement of affected areas of the body), and elephantiasis (long standing enlargement and swelling of the limbs, scrota, or breasts associated with skin thickening)." Addiss et al. 2005, Pg 3.
"The acute form of the disease is common and causes severe hardship in endemic communities. Infected individuals suffer from one to eight acute episodes per year, and during each episode, affected patients are bedridden for three to five days. Morbidity caused by chronic LF is mostly lifelong, and the disease is considered the second leading cause of disability in the world (WHO 1995b). Patients affected by elephantiasis or hydrocele are often victims of societal discrimination, and the disease impairs their educational and employment opportunities, marriage prospects, and sexual life." Jamison et al. 2006, Pg 436.
World Health Organization, "Disease and injury regional estimates for 2004: Prevalence for WHO regions" and "Disease and injury regional estimates for 2004: Deaths for WHO regions."
"Onchocerciasis is an eye and skin disease caused by a worm (filaria) known scientifically as Onchocerca volvulus. It is transmitted to humans through the bite of a blackfly (simulium species). These flies breed in fast-flowing streams and rivers, increasing the risk of blindness to individuals living nearby, hence the commonly known name of 'river blindness'." World Health Organization, "Onchocerciasis (River Blindness) - Disease Information."
- All symptoms: "Inflammation in the eyes leads to irreversible ocular lesions, resulting first in impaired vision and finally in total blindness (WHO 1995a). The death of microfilariae in the skin gives rise to intense itching, dermatitis, depigmentation, and atrophy of the skin (Murdoch and others 2002)." Jamison et al. 2006, Pg 435.
- Severity of skin disease:
- "The death of microfilariae is very toxic to the skin and the eye, producing terrible itching and various eye manifestations (lesions). After repeated years of exposure, these lesions may lead to irreversible blindness and disfigurative skin diseases sometimes named 'leopard' skin and 'lizard' skin." World Health Organization, "Onchocerciasis (River Blindness) - Disease Information."
- "Even though the importance of onchocercal blindness has long been recognized, only in 1995 did research demonstrate that the public health importance of onchocercal skin disease was even greater. Troublesome itching associated with dermal onchocerciasis makes working, studying, or interacting socially difficult (Murdoch and others 2002; Vlassoff and others 2000)." Jamison et al. 2006, Pg 437.
"The distribution of onchocerciasis is linked to the location of blackflies which are naturally found close to the fast-running streams and rivers in the inter-tropical zones. Therefore, about 90% of the disease occurs in Africa. Onchocerciasis is also found in six countries in Latin America and in Yemen in the Arabian Peninsula, where the disease is believed to be exported by the slave trade." World Health Organization, "Onchocerciasis (River Blindness) - Disease Information."
For information on Latin America, see our full report on The Carter Center's efforts to eliminate onchocerciasis there.
"Sanitation can also help prevent trachoma. More than 70 percent of the incidence of this infection has been shown to be caused by flies, mainly of the species Musca sorbens, which breeds preferentially in scattered human feces." Jamison et al. 2006, Pg 764.
"It is a bacterial infection caused by Chlamydia trachomatis that is associated with poverty and is most prevalent in hot dry areas. Repeated infections cause scarring of the conjunctiva of the upper eyelid, which causes the eyelid to turn in (entropion) so that the eyelashes touch the cornea at the front of the eye. This is known as trachoma trichiasis. Every movement of the eye or eyelids causes trauma to the corneal surface so that it eventually turns opaque and the person becomes blind." Yorston et al. 2006, Pg 2.
"This contact between one (or more) lashes and the surface of the eye is called trichiasis: movement of the eye or eyelids damages the corneal surface layer (corneal epithelium). Corneal opacification and resulting blindness probably develops primarily as a result of this trauma and secondary bacterial corneal infection." Yorston et al. 2006, Pg 3.
"Guinea worm disease is contracted when a person drinks stagnant water from a well or pond that is contaminated with tiny freshwater copepods carrying guinea worm larvae." Levine 2007, Pg 2.
Levine 2007, Pg 2.
"To ease the burning pain, infected individuals frequently submerge the blister in cool water, causing the blister's rupture and the release of hundreds of thousands of larvae into the water. A vicious cycle of reinfection occurs when sufferers inadvertently contaminate sources of drinking water and set the stage for themselves and other residents to contract the infection." Levine 2007, Pg 2.
"Guinea worm disease takes its toll not through death, as the disease is rarely fatal, but rather through devastating disability, pain, and infection. Two studies in Nigeria, for example, reported that 58 percent to 76 percent of patients were bedridden for at least one month following the worm's emergence. The pain is also long lasting, evidenced by the fact that in one study 28 percent of infected individuals in Ghana experienced pain 12 to 18 months later." Levine 2007, Pg 2.
Levine 2007, Pg 2.