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
HIV is a virus that is transmitted through sexual intercourse, contact with contaminated blood, or between a mother and child during birth or breastfeeding. The virus weakens an individual's immune system, making him or her susceptible to life-threatening diseases such as tuberculosis. UNAIDS estimates that the median time from HIV infection until death, without treatment, is 9-11 years. A review of eight developing-world studies estimated the median time from AIDS diagnosis to death as 6-19 months.
Tuberculosis (TB) is an infection that is contracted when individuals inhale airborne droplets (produced when infected individuals cough, sneeze, or even talk). All else equal, approximately 5% of those infected with TB develop the progressive form of the disease within five years of infection. 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.
Malaria is one of the leading causes of child deaths in Africa. It is transmitted from person to person by infected mosquitoes.
Malaria causes short-term illness and may cause death. Less frequently, it can cause permanent disability. It can also contribute to other problems such as anemia, low birthweight for babies of infected women, and growth retardation. It is often pointed to as a major economic burden.
Most malaria deaths occur in Africa, and the disease has its largest impact on young children. Pregnant women are also at increased risk of illness and death from malaria.
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.
|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. In sub-Saharan Africa, a child under 5 has, on average, over 3 episodes per year of diarrhea; in 2001, about 1.8 million children living in low- and middle-income countries died from diarrhea.
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 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. Pneumonia is an infectious disease and can be spread through bacteria, viruses, or fungi. Pneumonia causes difficult breathing, fever, and cough.
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. The World Health Organization (WHO) estimates that 1.8 million children under five die of pneumonia each year.
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. 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.
Diphtheria is spread through close physical contact, mainly through droplets produced from coughing and sneezing. Symptoms range from a sore throat to life-threatening respiratory infection. Diphtheria can also cause toxic damage to heart muscles and/or peripheral nerves.
The World Health Organization estimates between 5% and 10% of diphtheria patients die, even if properly treated. In countries still burdened with diphtheria, young children are most commonly affected. In industrialized countries, endemic diphtheria is extremely rare.
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. "Patients normally improve by the third day of rash, and are fully recovered 7–10 days from the onset of disease." More serious cases come about by measles complications such as malnutrition and permanent neurological disorders. Blindness, encephalitis, diarrhea, ear infection and pneumonia may also occur.
"In most industrialized nations, measles is well controlled or even eliminated." Measles continues to be a leading cause of death among young children, especially in Africa and south and east Asia. Case fatality rates are 5-15% in developing countries and .01%-.1% in developed countries.
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." 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." HBV can also cause a chronic liver infection that can later develop into cirrhosis of the liver or liver cancer.
"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." 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:
- 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. Following infection from a bite, a three to six day incubation period occurs before symptoms appear. Symptoms include intense headache, fever, chills, and myalgia. 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. Survivors usually experience complete recovery of the liver and kidneys.
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."
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."
"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."
Hib has been almost completely eliminated in the industrialized world and has been dramatically reduced in some parts of the developing world.
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. 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%.
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. "Most pertussis occurs in school-aged children in developing countries."
Tetanus is transmitted through spores that enter the body through wounds or the umbilical cord stump. The majority of cases are associated with childbirth and occur through unclean deliveries and poor post-natal hygiene, mainly in the developing world. 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.
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.
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:
- Trichuriasis: 26 million people
- Hookworm: 60 million people
- Ascariasis: 58 million people
They cause a variety of chronic symptoms:
- Chronic pain
STHs may also severely impair mental and physical growth in children. Hookworm in pregnant women causes premature births, low birth-weight, and impaired lactation. 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. "Many people infected remain asymptomatic; about 80% of infected children show early symptoms." 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.
- Urinary tract infections and other bladder problems at later stages, potentially leading to bladder cancer and kidney failure.
- Bloody diarrhea, bloody stools, abdominal pain, and liver failure.
- Anemia, malnutrition, and impaired growth and cognitive function in children with repeated infections.
- 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).
Lymphatic filariasis is caused by parasitic worms that are transmitted by mosquitoes. People can be infected but asymptomatic. Symptoms can include:
- 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.
Lymphatic filariasis primarily causes disability (as opposed to mortality):
- 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. The disease can ultimately result in low vision, blindness and/or severe skin disease associated with extreme itching.
Onchocerciasis is most common in Central and West Africa (90% of cases), but also occurs Latin America and parts of the Arabian Peninsula.
Trachoma is most commonly transmitted by flies.
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.
Dracunculiasis (aka guinea worm)
Guinea worm is transmitted when a person drinks contaminated water. 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." 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.
Guinea worm is rarely fatal, but it causes severe pain and debilitation, often leaving those infected bedridden for more than a month. "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."
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