Definition
Infectious diseases cause between 40 and 50 percent of all deaths in developing countries. For children younger than five years of age in these countries, infectious diseases cause almost 70 percent of deaths. Poverty, lack of education, inadequate or absent clean water and sanitation systems, crowded living conditions, unsafe sex, limited health care facilities, and lack of vaccines lead to the disproportionate burden of infectious diseases in the developing world. The chronic infectious disease-related disabilities suffered by adults in their prime working years leads to more poverty, continuing the cycle for the next generation.
Respiratory infections, including tuberculosis and pneumonias; diarrheal illnesses; malaria; and human immunodeficiency virus (HIV) contribute most to the infectious disease death toll in economically impoverished areas of the world; these and other infections, including the neglected tropical diseases, also contribute to substantial rates of chronic disease and disability.
Malaria
Malaria is a parasitic disease transmitted by the bite of the female
Anopholes mosquito, which is endemic to more than one hundred
countries, including areas of Africa, Southeast Asia, Central America, South
America, India, and parts of India and Oceania. Infection with any of the four
species of Plasmodium causes fever, chills, and muscle aches, but
the most dangerous kind of malaria, falciparum malaria, can cause
serious disease in all ages. It results in significant mortality in children
younger than five years of age.
The battle against malaria is fought on two fronts: with mosquito control and with effective antimalarial medication. In developing countries, there are many inherent difficulties with both methods. Mosquito control has historically been approached by widespread use of insecticides, including dichloro-diphenyl-trichloroethane (DDT). Because of worldwide bans on the use of DDT, other approaches have been taken, including very limited use of DDT.
The main mosquito-control tool in campaigns against malaria is the insecticide-treated bed net (ITN), which keeps mosquitoes away from people who are sleeping at night, the time when biting mosquitoes are most active. As of 2008, about 31 percent of African households in malarious areas had an ITN, and about 24 percent of children younger than the age of five slept under one. Several countries, including Rwanda, Tanzania, Eritrea, Sao Tome and Principe, Zambia, and Zanzibar, have achieved even higher ITN coverage, with a resultant 50 percent reduction in malaria cases and deaths in those areas. These significant improvements were aided by expanded international funding of malaria control programs to help meet the goal of the United Nations (UN) to decrease childhood mortality by two-thirds by 2015; this effort was part of the UN Millennium Development Goals program. In 2010, 145 million nets were distributed.
The other major goal of malaria control campaigns is the widespread
availability and use of artemisinin drugs to treat malaria.
Although older malaria drugs, such as quinine and chloroquine, are
inexpensive and available in most developing countries, the malaria parasites have
developed resistance to these drugs, rendering them ineffective in many areas of
the world. Artemisinin drugs, though more expensive, are much more effective as
long as they are used in combination with a second drug; otherwise, resistance
will quickly develop. The use of these combination drugs is called
artemisinin-based combined therapy (ACT). Because some signs of resistance to
artemisinins have been reported in Southeast Asia, the World Health
Organization is leading an initiative to carefully monitor
malarious countries for the presence of artemisinin resistance and to contain it
if found. International funding continues to go to agencies working on wider
access to artemisinins.
HIV and Tuberculosis
In 2014, more than thirty-six million people worldwide are infected with HIV, and a disproportionate number of them reside in developing countries. HIV is most prevalent in sub-Saharan Africa, and in that region; 70 percent of all HIV cases are in the region. In Africa, HIV is transmitted nearly exclusively by heterosexual sex. Culturally and socially, females lack the ability to protect themselves from diseases transmitted by male sex partners or by rape, which is a widespread practice in some areas.
As more girls and women become infected, more newborns will become infected with maternally transmitted HIV. Transmission also occurs through breast milk, which is the only economical way to nourish infants in many impoverished areas. Decreasing the risk of mother-to-child HIV transmission is possible and requires only one dose of an antiretroviral drug during labor and one dose for the newborn to reduce risk by about 40 percent. More complicated and probably more effective regimes require girls and women to take multiple drugs during late pregnancy and until breast-feeding ends, but these practices have been difficult to implement in many areas. Maternal and paternal deaths from acquired immunodeficiency syndrome (AIDS), the advanced stage of HIV infection, have resulted in an enormous increase in the number of so-called AIDS orphans in many areas of Africa. However, progress has been made: as of 2014, more than 70 percent of pregnant women with HIV were treated to prevent transmitting the disease to their babies.
Outside Africa, growing areas of concern are in Asia, especially in Thailand, Cambodia, Myanmar, and Vietnam. Contributing to dramatically increased rates of HIV infection in these areas are the female sex-worker trade, a lack of condom use, stigmatization of HIV testing, and the transient population.
A surge in the number of new cases of tuberculosis (TB) has accompanied the HIV epidemic in both developed and undeveloped countries, but the latter are particularly unprepared to deal with increases in this serious disease. Some of these cases represent strains of TB that are resistant to many of the existing tuberculosis drugs. Asymptomatic TB infection is common in developing countries; when a healthy person inhales Mycobacterium tuberculosis, the body effectively walls off the infection in the lung, and the infected person does not become ill or contagious. As that person is infected with HIV, which gradually destroys the immune system, however, inactive TB becomes active, causing cough, fever, weight loss, and death if untreated. Coinfection with HIV and TB is a disabling, deadly combination.
Treatment of TB requires accurate diagnosis, which is often unavailable in undeveloped areas, and also requires long-term compliance with a daily medication regimen. Both factors contribute to the increase in new infections and incompletely treated infections. With the HIV epidemic in these areas, tuberculosis has become a priority in many disease-control programs.
International efforts to contain both the HIV epidemic and the upsurge in TB have focused on prevention, testing, and treatment. Prevention has focused on safer-sex practices and the empowering of girls and women to avoid sexually transmitted infection. HIV testing has increased but remains problematic because testing is stigmatized, and the stigma increases for persons whose test results are positive.
Progress has been made in the availability of antiretroviral drugs for HIV treatment; according to UN AIDS, between 2006 and 2012, the number of people in sub-Saharan Africa receiving the drugs doubled.
Diarrheal Illness and Measles
Diarrheal illness and its nearly inevitable complications of dehydration
and malnutrition are large contributors to the disease burden in
developing countries, particularly in children younger than age five years. While
diarrhea is considered a minor, self-limiting illness in the developed world, in
undeveloped countries, diarrhea kills more children each year than HIV, measles,
and malaria combined. Diarrhea can be caused by many types of viruses, bacteria,
and protozoa, but it is mostly a result of impure drinking water and fecal
contamination of the living environment.
Even with access to decent sanitation and clean water, a child who does contract a diarrheal illness in a developing country is much less likely to have access to simple treatments that could save his or her life. One simple diarrhea treatment strategy that can save lives includes giving an ill child oral rehydration with a special salt solution (often referred to as ORS) and a zinc supplement, while continuing to feed the child to avoid malnutrition. WHO and other public health entities have also launched social marketing campaigns encouraging stigmatization of defecation in public (a significant problem in India, in particular) and encouraging handwashing with soap to avoid infection.
Immunization with rotavirus vaccine is another strategy
that can decrease diarrhea in children, but this vaccine has yet to be included in
immunization programs in developing countries. Better access to measles vaccine
might also reduce the number of deaths from childhood diarrhea, as diarrhea is
often a debilitating symptom of measles in very young children.
Measles is another childhood disease that affects children
in undeveloped countries significantly more than it does in developed countries,
primarily because, in developed countries, measles vaccination is routine at age
twelve to fifteen months (with a booster at school entrance in most developed
countries). Vaccination of young children in some areas of Africa and Asia has
been limited.
The Measles Initiative, a consortium including the American Red Cross, the United Nations Foundation, the Centers for Disease Control and Prevention (CDC), United Nations Children’s Fund (UNICEF), and WHO, had committed to reducing measles worldwide by 90 percent by 2010. Since 2000, the initiative has helped prevent 15.6 million deaths through vaccination. As a result, 84 percent of the world's children have been immunized. The biggest impact has been in Africa, and in the eastern Mediterranean region, which includes Afghanistan, Iran, Iraq, Pakistan, and Somalia.
For children not immunized and who are infected with measles, the disease can
manifest as a mild respiratory infection, or it can be a serious illness. Serious
complications of the infection include pneumonia, ear infection, blood
abnormalities, and encephalitis (inflammation of the
brain), which can cause permanent neurologic effects or death.
Neglected Tropical Diseases
Neglected tropical diseases (NTDs) infect billions of people worldwide, yet they are often unknown in developed countries. As a result, less funding has gone to NTDs for disease control or elimination programs. In the later decades of the twentieth century, the attention to NTDs increased somewhat. The NTDs contributing the largest burden of disease are lymphaticfilariasis (elephantiasis), onchocerciasis (river blindness), schistosomiasis, soil-transmitted helminth (worm) infections, and trachoma.
Lymphatic filariasis (LF) is a disfiguring disease caused by thin, microscopic
worms and is transmitted by mosquito bites. The tiny worms live in and damage the
lymphatic system and, after long periods of time, can result in severe swelling of
the arms, legs, breasts, and genitalia, leading to substantial disability. When
chronically swollen areas become thickened and hardened, the resultant condition
is referred to as elephantiasis. LF affects a minimum of one billion people in
eighty-three countries, primarily in tropical and subtropical areas of India,
Indonesia, Bangladesh, and Nigeria. LF can be treated with annual doses of
inexpensive antiparasitic drugs, including albendazole and diethylcarbazine, which
do not kill adult worms in the body but kill the immature worms that can transmit
the disease person-to-person through mosquito bites and thereby interrupt the
cycle of transmission.
Onchocerciasis, also known as river blindness, is
transmitted from person to person by the bite of a black fly; the disease affects
eighteen million people in thirty-five countries. The disease causes skin rashes
with intense itching and eye damage that can result in blindness. An annual dose
of the drug ivermectin can prevent the disease.
Schistosomiasis affects two hundred million people in
seventy-four countries. It is caused by a parasite called a fluke, which lives in
fresh-water snails and causes several different syndromes in humans; these
syndromes can result in kidney, bladder, and liver disease, and death.
Soil-transmitted helminths (worms) cause malnutrition, vitamin deficiencies, anemia, and intestinal obstruction in more than one billion people worldwide, with many more persons at risk. It is easily treated by administration of mebendazole or albendazole twice yearly. Partners for Parasite Control, a WHO group, is working toward the goal of treating 75 percent of all at-risk children with these drugs.
Trachoma is a bacterial infection of the eye caused by
Chlamydia trachomatis, which causes scarring of the lining of
the upper eyelid and leads to blindness. It is spread from person to person by
direct contact and affects more than eighty-four million people in fifty-five
countries. The International Trachoma Initiative is dedicated to eradicating this
disease by using a treatment and prevention strategy known as SAFE: surgery,
antibiotics, face-washing hygiene, and environmental changes.
Impact
Infectious diseases in developing countries remain a huge global problem. Recognizing their responsibility to respond in a humanitarian way, many of the wealthy nations of the world are committed to finding solutions to these diseases. WHO, the Global Health Council, UNICEF, and other international organizations are working toward disease eradication, with polio and measles the most likely initial targets for eradication. National efforts, such as the US President’s Emergency Plan for AIDS Relief (PEPFAR), which was reauthorized in 2008, will continue to pump economic aid to programs that are researching ways to control HIV/AIDS, tuberculosis, malaria, and other diseases around the world.
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