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.

HIV/AIDS

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, eventually leading to death.2 UNAIDS estimates that the median time from HIV infection until death, without treatment, is 9-11 years.3 A review of eight developing-world studies estimated the median time from AIDS diagnosis to death as 6-19 months.4

Tuberculosis

Tuberculosis (TB) is an infection that is contracted when individuals inhale airborne droplets (produced when infected individuals cough, sneeze, or even talk).5 All else equal, approximately 5% of those infected with TB develop the progressive or "smear-positive" form of the disease.6 According to the Disease Control Priorities (DCP) report,

About two thirds of untreated smear-positive patients [those with the most infectious form of the disease] will die within five to eight years, the majority within the first 18 months. The case-fatality rate for untreated smear-negative cases is lower, but still of the order of 10 to 15 percent.7

Malaria

Malaria is one of the leading causes of child deaths in Africa.8 It is transmitted from person to person by infected mosquitoes.9

Malaria causes short-term illness and often death. Less frequently, it can cause permanent mental impairment.10 It can also contribute to other problems such as anemia, low birthweight for babies of infected women, and growth retardation.11 It is often pointed to as a major economic burden.12

Malaria is predominantly a problem in Africa,13 and has its largest impact on young children. The table below summarizes its largest consequences; note that the bottom two rows indicate an average of over 4 days sick per year for children under 5.14

Diarrhea

Diarrhea in young children living in poverty can be so severe that it results in death by dehydration (usually this only occurs in children under five). In sub-Saharan Africa, on average, a child under 5 had 3-5 episodes per year of diarrhea;15 in 2001, 1.6 million children living in low- and middle-income countries died from diarrhea.16

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). 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 infrastructure programs.

Pneumonia

Pneumonia is a lower-respiratory infection, infecting all ages, but mostly children and the elderly. Most cases are due to infection by bacteria or viruses, and a few are due to inhalation of chemicals or trauma to the chest. Pneumonia causes chest pain, shortness of breath, fever, cough, and night sweats. 17

In developing countries, the case-fatality rate in children with viral pneumonia ranges from 1.0 to 7.3 percent, with bacterial pneumonia from 10 to 14 percent and with mixed viral and bacterial infections from 16 to 18 percent. 18 The World Health Organization (WHO) estimates that 2 million children under five die of pneumonia each year.19

Vaccine-preventable diseases

Poliomyelitis

Poliomyelitis (polio) is a highly infectious disease, which mainly affects children under the age of 5. The virus is transmitted through contaminated food and water. Initial symptoms of polio include fever, fatigue, headache, vomiting, stiffness in the neck, and pain in the limbs. 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.20The WHO estimates currently a low rate of incidence, about 250-550 cases per year. In 2008, only four countries in the world remain polio-endemic: Afghanistan, India, Nigeria and Pakistan. 21

Diphtheria

Diphtheria is spread through droplets and close physical contact, mainly through droplets produced from coughing and sneezing.22Transmission period occurs for under two weeks and usually affects the tonsils, pharynx, larynx and occasionally the skin. Symptoms range from a sore throat to life-threatening diphtheria of the larynx or of the lower and upper respiratory tracts. Diphtheria can also cause toxic damage to heart muscles and/or peripheral nerves.

WHO estimates between 5% and 10% of diphtheria patients die, even if properly treated.23

In countries still burdened with diphtheria, young children are most commonly affected. In industrialized countries, endemic diphtheria is extremely rare.24

Measles

The measles virus is a highly contagious disease transmitted by respiratory droplets, aerosol and/or direct contact. Initial symptoms appear 8-12 days after exposure to virus, and include high fever, runny nose, bloodshot eyes and tiny white spots on the inside of the mouth. A rash becomes visible after 7-18 days.25 "Patients normally improve by the third day of rash, and are fully recovered 7–10 days from the onset of disease."26 More serious cases come about by measles complications such as malnutrition and permanent neurological disorders. Blindness, encephalitis, severe diarrhea, ear infection and pneumonia might also occur.27

"In most industrialized nations, measles is well controlled or even eliminated."28 Measles continues to be a leading cause of death among young children, especially in Africa and south and east Asia.29 Case fatality rates are 5-15% in developing countries and .01%-.1% in developed countries.30

Hepatitis B

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). "Common modes of transmission include mother-to-infant, child-to-child, unsafe injection practices, blood transfusions and sexual contact."31. 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."32 HBV can also cause a chronic liver infection that can later develop into cirrhosis of the liver or liver cancer. Up to lifelong carriage and transmission can occur.

"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."33 The WHO's Position Paper on Hepatitis B examines differences in contraction and mortality rates as determined by the mode of transmission and age:34

• 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..
• Chronic HBV related cirrhosis and hepatocellular cancer kills about .135%-.225% of HBV infected infants, .045%-075% of infected children, and .009%-.015% of infected adults, causing an estimated 500,000-700,000 deaths annually.
• 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

Yellow fever is a virus spread by infected mosquitoes.35 Following infection from a bite, a three to six day incubation period occurs before symptoms appear.36 Symptoms include intense headache, fever, chills, and myalgia.37 Serious cases occur in 15% of cases, causing symptoms such as jaundice, liver and kidney failure and cardiovascular collapse. Kidney function also deteriorates, causing problems ranging from abnormal protein levels in the urine to complete kidney failure with no urine production. About 20-50% of patients with liver or kidney failure die, in most cases 7-10 days after onset of disease.38 Survivors usually experience complete recovery of the liver and kidneys. 39

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 15° north and 15° south of the equator."40

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."41

"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."42

Hib is almost completely eliminated in the industrialized world and has been dramatically reduced in some parts of the developing world.43

Pertussis

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.44 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.45 The overall case-fatality rate is up to 10% in infants and children. 46

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.47"Most pertussis occurs in school-aged children in developing countries."48

Tetanus

Tetanus may affect any age group. Tetanus is transmitted through spores that enter the body through wounds or the umbilical cord stump.49The majority of cases are birth-associated and occur through unclean deliveries and poor post-natal hygiene, mainly in the developing world. 50 Symptoms 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.51

Neglected tropical diseases

"Neglected tropical diseases" are a specific set of chronic infectious diseases found primarily in tropical areas,52 and do not include such well-known diseases as AIDS, tuberculosis and malaria.

Soil-transmitted helminths

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:53

• Trichuriasis - 26m people
• Hookworm - 60m people
• Ascariasis - 58m people

They cause a variety of chronic symptoms:54

• Chronic pain
• Anemia
• Diarrhea
• Undernutrition

STHs also severely impair mental and physical growth in children.55 Hookworm in pregnant women causes premature births, low birth-weight, and impaired lactation.56 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

Schistosomiasis is caused by flatworms, called schistosomes, and passed through infested water.57 "Many people infected remain asymptomatic; about 80% of infected children show early symptoms."58 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.59
• Urinary tract infections and other bladder problems at later stages, potentially leading to bladder cancer and kidney failure.60
• Bloody diarrhoea, bloody stools, abdominal pain, and liver failure.61
• Anemia, malnutrition, and impaired growth and cognitive function in children with repeated infections.62
• Death. There is large disagreement about the number of annual fatalities due to schistosomiasis-caused non-functioning kidneys and hematemesis (estimates range from 27,000 to 280,000).63

Lymphatic filariasis

Lymphatic filariasis is caused by parasitic worms that are transmitted by mosquitoes.64 People can be infected but asymptomatic.65 Symptoms can include:66

• 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.67

Lymphatic filariasis primarily causes disability (as opposed to mortality):68

• 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.69 The disease can ultimately result in low vision, blindess and/or severe skin disease associated with extreme itching.70 The WHO estimates that approximately 500,000 people worldwide are blind due to onchocerciasis.71

Onchocerciasis is most common in Central and West Africa (90% of cases), but also occurs Latin America and parts of the Arabian Peninsula.72

Trachoma

Trachoma can be passed in several ways: flies, touching eyes, and through clothes and other household linens.73

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.74

Dracunculiasis (aka guinea worm)

Guinea worm is transmitted when a person drinks contaminated water.75 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."76 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.77

Guinea worm is rarely fatal, but it causes severe pain and debilitation, often leaving those infected bedridden for more than a month.78 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.79

Sources

• Addiss, D., et al. 2005. "Albendazole for lymphatic filariasis." Cochrane Database of Systematic Reviews. Summary available online, accessed 7/7/09.
• Christianson, A., C. Howson, and B. Modell. 2006. "March of Dimes Global Report on Birth Defects: The Hidden Toll of Dying and Disabled Children." March of Dimes.
• Danso-Appiah, A., et al. 2008. "Drugs for treating urinary schistosomiasis." Cochrane Database of Systematic Reviews. Summary available online, accessed 7/7/09.
• The Disease Control Priorities (DCP) Project. 2006. "Disease Control Priorities in Developing Countries (2nd Edition)." Available online, accessed 7/7/2009.
• Karmacharya, Jagajan. 2009. "Cleft Lip." Emedicine.com. Available online, accessed 7/7/2009.
• Levine, Ruth. 2004. "Case Study 11: Reducing Guinea Worm in Asia and Sub-Saharan Africa." Millions Saved: Proven Success in Global Health. Center for Global Development. Available online (PDF), accessed 7/7/09.
• Lengeler C. 2004. "Insecticide-treated bed nets and curtains for preventing malaria." Cochrane Database of Systematic Reviews. Summary available online, accessed 7/7/09.
• Mathers, C.D., M. Ezzati, and A.D. Lopez. 2007. "Measuring the burden of neglected tropical diseases: the global burden of disease framework." PLoS Negl. Trop. Dis. 1:e114. Available online, accessed 7/7/09.
• Sachs, J.D., and John Luke Gallup. 2000. "The Economic Burden of Malaria." CID Working Paper No. 052. Available online, accessed 7/7/09.
• Saconato, H., and Á.N. Atallah. 1999. "Interventions for treating schistosomiasis mansoni." Cochrane Database of Systematic Reviews. Summary available online, accessed 7/7/09.
• UNAIDS Reference Group on Estimates, Modelling, and Projections. 2006. "Improving parameter estimation, projection methods, uncertainty estimation, and epidemic classification." Available online at http://data.unaids.org/pub/Report/2007/2006prague_report_en.pdf, accessed 7/21/09.
• WHO Global Burden of Disease (GBD) Project. 2004. "Disease and injury regional estimates for 2004." Data available online, accessed 7/7/09.
• World Health Organization (WHO). 2003a. "Introduction of inactivated poliovirus vaccine into oral poliovirus vaccine-using countries." Weekly epidemiological record. Available online (PDF), accessed 7/7/09.
• World Health Organization (WHO). 2003b. "Yellow fever vaccine: WHO Position Paper." Weekly epidemiological record. Available online (PDF), accessed 7/8/09.
• World Health Organization (WHO). 2004a. "Hepatitis B vaccine: Who Position Paper." Weekly epidemiological record. Available online (PDF), accessed 7/8/09
• World Health Organization (WHO). 2004b. "Measles vaccines: WHO Position Paper." Weekly epidemiological record. Available online (PDF), accessed 7/8/09.
• World Health Organization (WHO). 2005. "Pertussis vaccines: WHO Position Paper." Weekly epidemiological record. Available online (PDF), accessed 7/8/09.
• World Health Organization (WHO). 2006a. "Diphtheria vaccine: WHO Position Paper." Weekly epidemiological record. Available online (PDF), accessed 7/8/09.
• World Health Organization (WHO). 2006b. "Tetanus vaccine: WHO Position Paper." Weekly epidemiological record. Summary available online, accessed 7/7/09.
• 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." Available online at http://data.unaids.org/pub/Periodical/2006/zwahlen_unaids_hq_05_422204_2..., accessed 7/21/09.

1. 1.

   "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." http://www.who.int/topics/hiv_aids/en/, accessed 7/7/09.

2. 2.

   "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. The most advanced stage of HIV infection is acquired immunodeficiency syndrome (AIDS). It can take 10-15 years for an HIV-infected person to develop AIDS; antiretroviral drugs can slow down the process even further." http://www.who.int/topics/hiv_aids/en/, accessed 7/7/09.

3. 3.

   "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 2006, Pg 7-8.

4. 4.

   "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 2006, Pg 5.

5. 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." DCP 2006, Pg 290.

6. 6.

   "In the absence of other predisposing conditions, only about 5 percent of infected people develop progressive primary disease within five years of infection (Comstock, Livesay, and Woolpert 1974; Sutherland 1968, 1976)." DCP 2006, Pg 290.

7. 7.

   DCP 2006, Pg 291.

8. 8.

   "In Africa, malaria accounts for an estimated 25% of all childhood mortality below age five, excluding neonatal mortality (WHO 2003)." Lengeler 2004, Pg 3.

9. 9.

   "Four species of the genus Plasmodium cause malarial infections in humans: P. falciparum, P. vivax, P. ovale, and P. malariae. Virtually all deaths are caused by falciparum malaria. 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." DCP 2006, Pg 413.

10. 10.

    See DCP 2006, Pg 416, Table 41.3. For estimates of cases of hearing impairment, visual impairment, epilepsy, etc. caused by malaria.

11. 11.

    "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)." DCP 2006, Pg 417.

12. 12.

    Sachs 2000.

13. 13.

    See DCP 2006, Pg 415, Table 21.1. For a summary of the burden of malaria in Africa vs. elsewhere.

14. 14.

    Number of episodes, days of illness, and malaria mortality come from DCP 2006, Pg 416. Population for Africa comes from the Global Burden of Disease Project, Mortality by Region.

15. 15.

    http://www.dcp2.org/pubs/DCP/19/Figure/19.1, accessed 7/7/09.

16. 16.

    http://www.dcp2.org/pubs/GBD/3/Table/3.B1, accessed 7/7/09.

17. 17.

    See "WebMD: Pneumonia, Topic Overview" at http://www.webmd.com/a-to-z-guides/pneumonia-topic-overview, accessed 7/7/09.

18. 18.

    "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)." DCP 2006, Pg 485.

19. 19.

    "The World Health Organization (WHO) estimates that 2 million children under five die of pneumonia each year." DCP 2006, Pg 483.

20. 20.

    WHO 2003a.

21. 21.

    WHO 2003a.

22. 22.

    "Transmission occurs only through droplets and close physical contact." DCP 2006, Pg 25.

23. 23.

    "In countries endemic for diphtheria, the disease occurs mostly as sporadic cases or in small outbreaks. Although most infections with C. diphtheriae are asymptomatic or run a relatively mild clinical course, high case-fatality rates (>10%) have been reported even in recent outbreaks." WHO 2006a, Pg 27.

24. 24.

    "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." DCP 2006, Pg 25.

25. 25.

    "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. The average interval from exposure to onset of rash is 14 days (range 7–18 days); patients are contagious from 2–3 days before until 1–2 days after onset of the rash. Persistent infection does not normally occur. Individuals also suffer from measle complications such as malnutrition and neurological disorders." WHO 2004b, Pg 132.

26. 26.

    WHO 2004, Pg 113.

27. 27.

    "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." DCP 2006, Pg 395.

28. 28.

    WHO 2004b, Pg 130.

29. 29.

    "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." WHO 2004b, Pg 132.

30. 30.

    WHO 2004b, Pg 134.

31. 31.

    WHO 2004a, Pg 257.

32. 32.

    http://www.who.int/mediacentre/factsheets/fs204/en/, accessed 7/8/09.

33. 33.

    WHO 2004a, Pg 257.

34. 34.

    WHO 2004a.

35. 35.

    "Exposure of susceptible persons to bites from infected mosquitoes is the only significant mode of YF transmission." http://www.who.int/biologicals/areas/vaccines/yellow_fever/yellow_fever_..., accessed 7/8/09.

36. 36.

    "Yellow fever virus is transmitted by mosquitoes, primarily Aedes eqypti, with a three-to six-day incubation period." DCP 2006, Pg 396.

37. 37.

    "Patients present with intense headache, fever, chills, and myalgia, among other symptoms." DCP 2006, Pg 396.

38. 38.

    "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." WHO 2003b, Pg 353.

39. 39.

    WHO 2003b, Pg 354.

40. 40.

    WHO 2003b, Pg 351.

41. 41.

    DCP 2006, Pg 396.

42. 42.

    WHO 2003b, Pg 447.

43. 43.

    "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." WHO 2003b, Pg 446.

44. 44.

    "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." WHO 2005, Pg 33.

45. 45.

    In young infants, pertussis may cause only apnoea and cyanosis, whereas in adolescents and adults, uncharacteristic, persistent cough may be the only manifestation of the disease. The catarrhal, paroxysmal and convalescent stages of the disease may last for a total of 1 to several months. Complications occur in 5–6% of pertussis cases, most frequently in infants aged <6 months." WHO 2005, Pg 33.

46. 46.

    See DCP 2006, Pg 90, Table 20.1.

47. 47.

    WHO 2005, Pg 35.

48. 48.

    DCP 2006, Pg 394.

49. 49.

    DCP 2006, Pg 390, Table 20.1.

50. 50.

    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. WHO 2006b, Pg 200.

51. 51.

    "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." WHO 2006b, Pg 201.

52. 52.

    See Public Library of Science: Neglected Tropical Diseases http://www.plosntds.org/static/scope.action, accessed 7/8/09.

53. 53.

    Mathers 2007, Pg 8.

54. 54.

    "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)." DCP 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.

55. 55.
    • "Chronic STH infections resulting from Ascaris, Trichuris, and hookworm can dramatically affect physical and mental development in children (WHO 2002)." DCP 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." DCP 2006, Pg 467.

56. 56.

    "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)." DCP 2006, Pgs 467-8.

57. 57.

    "The major forms of human schistosomiasis are caused by five species of water-borne flatworm, or blood flukes, called schistosomes.... Schistosomes enter the body through contact with infested surface water. This particularly affects people engaged in agriculture and fishing. But rural-urban migration is introducing the disease into peri-urban areas in northeast Brazil and Africa, and refugee movements are spreading it to other areas. More tourists are contracting schistosomiasis with the rise in eco-tourism and travel off the beaten track, at times with severe acute infection and unusual problems including paralysis of the legs." http://www.who.int/mediacentre/factsheets/fs115/en/index.html, accessed 7/8/09.

58. 58.

    Danso-Appiah 2008, Pg 3.

59. 59.

    "Haematuria (blood in urine) and dysuria (painful urination) are the main early symptoms of the disease." Danso-Appiah 2008, Pg 3.

60. 60.

    "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 2008, Pg 3.

61. 61.

    "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 1999, Pg 3.

62. 62.

    "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 2008, Pg 3.

63. 63.

    "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." DCP 2006, Pg 470.

64. 64.

    "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. " http://www.who.int/mediacentre/factsheets/fs102/en/, accessed 7/8/09.

65. 65.

    "Infected people can harbor microfilaremia without overt clinical manifestations." DCP 2006, Pg 434.

66. 66.

    "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 2005, Pg 3.

67. 67.

    "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." DCP 2006, Pg 436.

68. 68.

    Global Burden of Disease Project 2004.

69. 69.

    "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'." http://www.who.int/blindness/partnerships/onchocerciasis_disease_informa..., accessed 7/9/09.

70. 70.
    • 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)." DCP 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." http://www.who.int/blindness/partnerships/onchocerciasis_disease_informa..., accessed 7/9/09.
      • "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)." DCP 2006, Pg 437.

71. 71.

    "It is estimated that there are about half a million blind people due to river blindness." http://www.who.int/blindness/causes/priority/en/index3.html, accessed 7/8/09.

72. 72.

    "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." http://www.who.int/blindness/partnerships/onchocerciasis_disease_informa..., accessed 7/8/09.

    For information on Latin America, see our full report on The Carter Center's efforts to eliminate onchocerciasis there.

73. 73.

    See http://www.who.int/blindness/causes/priority/en/index2.html, accessed 7/9/09.

74. 74.

    "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 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 2006, Pg 3.

75. 75.

    "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 2004, Case 11, Pg 2.

76. 76.

    Levine 2004, Case 11, Pg 2.

77. 77.

    "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 2004, Case 11, Pg 2.

78. 78.

    "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. 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." Levine 2004, Case 11, Pg 2.

79. 79.

    See Levine 2004, Case 11, Pg 2.