Bronchiolitis

Definition

Bronchiolitis is an acute viral infection of the small air passages of the lungs called the bronchioles.

 

Description

Bronchiolitis is extremely common. It occurs most often in children between the ages of two and 24 months, with peak infection occurring between three and six months of age. About 25% of infants have bronchiolitis during their first year, and 95% have had the disease by their second birthday. In temperate climates, bronchiolitis peaks from winter to late spring. In subtropical climates, the disease peaks from October to February.

Children who attend daycare or who live in crowded conditions and those who are exposed to second-hand smoke at home are more likely to develop bronchiolitis. Premature infants and children born with heart and lung defects or HIV/AIDS are more likely to have severe, life-threatening infections. Bronchiolitis occurs more often in boys than girls, with boys being hospitalized at 1.5 times the rate of girls. Bronchiolitis is a significant cause of respiratory disease worldwide. The World Health Organization (WHO) has funded research to develop a vaccine against the disease, but thus attempts have been unsuccessful.

Influenza

Definition

Usually referred to as the flu or grippe, influenza is a highly infectious respiratory disease. The disease is caused by certain strains of the influenza virus. When the virus is inhaled, it attacks cells in the upper respiratory tract, causing typical flu symptoms such as fatigue, fever and chills, a hacking cough, and body aches. Influenza victims are also susceptible to potentially life-threatening secondary infections. Although the stomach or intestinal "flu" is commonly blamed for stomach upsets and diarrhea, the influenza virus rarely causes gastrointestinal symptoms. Such symptoms are most likely due to other organisms such as rotavirus, Salmonella, Shigella, or Escherichia coli.

Description

The flu is considerably more debilitating than the common cold. Influenza outbreaks occur suddenly, and infection spreads rapidly. The annual death toll attributable to influenza and its complications averages 20,000 in the United States alone. In the 1918–1919 Spanish flu pandemic, the death toll reached a staggering 20-40 million worldwide. Approximately 500,000 of these fatalities occurred in America.

Influenza outbreaks occur on a regular basis. The most serious outbreaks are pandemics, which affect millions of people worldwide and last for several months. The 1918–1919 influenza outbreak serves as the primary example of an influenza pandemic. Pandemics also occurred in 1957 and 1968 with the Asian flu and Hong Kong flu, respectively. The Asian flu was responsible for 70,000 deaths in the United States, while the Hong Kong flu killed 34,000.

Cough

Definition

A cough is a forceful release of air from the lungs that can be heard. Coughing protects the respiratory system by clearing it of irritants and secretions.

Description

While people can generally cough voluntarily, a cough is usually a reflex triggered when an irritant stimulates one or more of the cough receptors found at different points in the respiratory system.

These receptors then send a message to the cough center in the brain, which in turn tells the body to cough. A cough begins with a deep breath in, at which point the opening between the vocal cords at the upper part of the larynx (glottis) shuts, trapping the air in the lungs. As the diaphragm and other muscles involved in breathing press against the lungs, the glottis suddenly opens, producing an explosive outflow of air at speeds greater than 100 mi (160 km) per hour.

cryptococcosis

Definition

Cryptococcosis is an infection caused by inhaling the fungus Cryptococcus neoformans. It is one of the diseases most often affecting AIDS patients. Cryptococcosis may be limited to the lungs, but frequently spreads throughout the body. Although almost any organ can be infected, the fungus is often fatal if it infects the nervous system where it causes an inflammation of the membranes covering the brain and spinal cord (meningitis).

Description

The fungus causing cryptococcis, C. neoformans, is found worldwide in soil contaminated with pigeon or other bird droppings. It has also been found on unwashed raw fruit. Cryptococcosis is a rare disease in healthy individuals, but is the most common fungal infection affecting people with AIDS.

People with Hodgkin's disease or who are taking large doses of drugs that suppress the functioning of the immune system (corticosteroids, chemotherapy drugs) are also more susceptible to cryptococcal infection. Cryptococcosis is also called cryptococcal meningitis (when the brain is infected), BusseBuschke disease, European blastomycosis, torular meningitis, or torulosis.

Avian Tuberculosis

A strain of tuberculosis in birds, caused by Mycobacterium avium. Birds consistently shed large amounts of the bacteria into the environment via feces. The organism is also pathogenic in humans and is especially problematic in the immunocompromised, such as those with human immunodeficiency virus infection.

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Tuberculosis [too-ber´ku-lo´sis]

An infectious, inflammatory, reportable disease that is chronic in nature and usually affects the lungs (pulmonary tuberculosis), although it may occur in almost any part of the body. The causative agent is Mycobacterium tuberculosis (also known as the tubercle bacillus). Formerly, the only other species of Mycobacterium thought to be pathogenic to humans were M. bovis and M. avium. It is now known that other species can produce diseases similar to true tuberculosis, including M. intracellulare, M. kansasii, M. simiae, and M. szulgai.

The most common mode of transmission of tuberculosis in the United States is inhalation of infected droplet nuclei. In some other parts of the world bovine tuberculosis, which is carried by unpasteurized milk and other dairy products from tuberculous cattle, is more prevalent. A rare mode of transmission is by infected urine, especially for young children using the same toilet facilities. Tuberculosis is also seen as an opportunistic infection in human immunodeficiency virus (HIV) infection.

Fluke Infections

Definition

Fluke infections are diseases of the digestive tract and other organ systems caused by several different species of parasitic flatworms (Trematodes) that have complex life cycles involving hosts other than human beings. Trematode comes from a Greek word that means having holes and refers to the external suckers that adult flukes use to draw nourishment from their hosts. Fluke infections are contracted by eating uncooked fish, plants, or animals from fluke-infected waters. Symptoms vary according to the type of fluke infection.

Description

In humans, fluke infections can be classified according to those diseases caused by liver flukes and those caused by lung flukes. Diseases caused by liver flukes include fascioliasis, opisthorchiasis, and clonorchiasis. Cases of liver fluke infection have been reported in Europe and the United States, as well as the Middle East, China, Japan, and Africa. Diseases caused by lung flukes include paragonimiasis. Paragonimiasis is a common infection in the Far East, Southeast Asia, Africa, Central and South America, Indonesia, and the Pacific Islands. It is estimated that between 40 million and 100 million people worldwide suffer from either liver or lung fluke infections.

In their adult stage, liver and lung flukes are symmetrical in shape, ranging between 1/4-1 in in length, and look somewhat like long, plump leaves or blades of grass. They enter through the mouth and can infect any person at any age.

Causes and symptoms

The symptoms of fluke infection differ somewhat according to the type of fluke involved. All forms of liver and lung fluke infection, however, have the following characteristics:

• most persons who get infected do not develop symptoms (asymptomatic)
• the early symptoms of an acute fluke infection are not unique to these diseases alone (nonspecific symptoms)
• infection does not confer immunity against re-infection by the same species or infection by other species of flukes
• infection is usually associated with eating uncooked fish, plants, or animals that live in fresh water

Asthma

Definition

Asthma is a chronic (long-lasting) inflammatory disease of the airways. In those susceptible to asthma, this inflammation causes the airways to spasm and swell periodically so that the airways narrow. The individual then must wheeze or gasp for air. Obstruction to air flow either resolves spontaneously or responds to a wide range of treatments, but continuing inflammation makes the airways hyper-responsive to stimuli such as cold air, exercise, dust mites, pollutants in the air, and even stress and anxiety.

Description

According to the American Lung Association, as of 2007, about 34.1 million Americans, including 9 million children, had been diagnosed with asthma during their lifetime. This number appears to be both increasing, especially among children under age 6, while at the same time the disease is becoming more severe. Asthma is estimated to cause between 3,500 and 5,000 deaths annually in the United States. In 2007, it was responsible for 217,000 emergency room visits and 10.4 million office visits. Its estimated cost to the United States economy is $19.7 billion. Worldwide, asthma is estimated to affect 300 million people. Asthma is closely linked to allergies; about 75% of people with asthma also have allergies.
The changes that take place in the lungs of people with asthma makes the airways (the "breathing tubes," or bronchi and the smaller bronchioles) hyper-reactive to many different types of stimuli that do not affect healthy lungs. In an asthma attack, the muscle tissue in the walls of bronchi go into spasm, and the cells lining the airways swell and secrete mucus into the airways. Both these actions cause the bronchi to become narrowed (bronchoconstriction). As a result, an asthmatic person has to make a much greater effort to breathe in air and to expel it.
Cells in the bronchial walls, called mast cells, release certain substances that cause the bronchial muscle to contract and stimulate mucus formation. These substances, which include histamine and a group of chemicals called leukotrienes, also bring white blood cells into the area, which is a key part of the inflammatory response. Many individuals with asthma are prone to react to such "foreign" substances as pollen, house dust mites, or animal dander; these substances are called allergens. On the other hand, asthma affects many individuals who are not allergic in this way.
About two-thirds of all cases of asthma are diagnosed in people under age 18, but asthma also may first appear during adult years. While the symptoms may be similar, certain important aspects of asthma differ in children and adults.

Histoplasmosis

Definition

Histoplasmosis is an infectious disease caused by inhaling the microscopic spores of the fungus Histoplasma capsulatum. The disease exists in three forms. Acute or primary histoplasmosis causes flulike symptoms. Most people who are infected recover without medical intervention. Chronic histoplasmosis affects the lungs and can be fatal. Disseminated histoplasmosis affects many organ systems in the body and is often fatal, especially to people with acquired immunodeficiency syndrome (AIDS).

Description

Histoplasmosis is an airborne infection. The spores that cause this disease are found in soil that has been contaminated with bird or bat droppings. In the United States, the disease is most common in eastern and midwestern states and is widespread in the upper Mississippi, Ohio, Missouri, and St. Lawrence river valleys. Sometimes histoplasmosis is called Ohio Valley disease, Central Mississippi River Valley disease, Appalachian Mountain disease, Darling's disease, or Histoplasma capsulatum infection.

Anyone can get histoplasmosis, but people who come in contact with bird and bat excrement are more likely to be infected. This includes farmers, gardeners, bridge inspectors and painters, roofers, chimney cleaners, demolition and construction workers, people installing or servicing heating and air conditioning units, people restoring old or abandoned buildings, and people who explore caves.

The very young and the elderly, especially if they have a pre-existing lung disease or are heavy smokers, are more likely to develop symptoms that are more severe. People who have a weakened immune system, either from diseases such as AIDS or leukemia, or as the result of medications they take (corticosteroids, chemotherapy drugs), are more likely to develop chronic or disseminated histoplasmosis.

Blastomycosis

Definition

Blastomycosis is an infection caused by inhaling microscopic particles (spores) produced by the fungus Blastomyces dermatitidis. Blastomycosis may be limited to the lungs or also involve the skin and bones. In its most severe form, the infection can spread throughout the body and involve many organ systems (systemic).

Description

Blastomycosis is a fungal infection caused by Blastomyces dermatitidis. Although primarily an airborne disease, farmers and gardeners may become infected from contact with spores in the soil through cuts and scrapes. The fungus that causes the disease is found in moist soil and wood in the southeastern United States, the Mississippi River valley, southern Canada, and Central America. Blastomycosis is also called Gilchrist's disease, Chicago disease, or North American blastomycosis. Another South and Central American disease, paracoccidioidomycosis, is sometimes called South American blastomycosis, but despite the similar name, this disease is substantially different from North American blastomycosis. Canine blastomycosis, a common dog disease, is caused by the same fungus that infects humans. However, people do not get this disease from their dogs except only very rarely through dog bites.

Blastomycosis is a rare disease infecting only about 4 in every 100,000 people. It is at least six times more common in men than in women and tends to more often infect children and individuals in the 30-50 year old age group. People who have diabetes mellitus or who are taking drugs that suppress the immune system (immunocompromised) are more likely to develop blastomycosis. Although people with AIDS can get blastomycosis because of their weakened immune system, blastomycosis has not been one of the more common fungal infections associated with AIDS.

Silicosis

Definition

Silicosis is a progressive disease that belongs to a group of lung disorders called pneumoconioses. Silicosis is marked by the formation of lumps (nodules) and fibrous scar tissue in the lungs. It is the oldest known occupational lung disease, and is caused by exposure to inhaled particles of silica, mostly from quartz in rocks, sand, and similar substances.

Description

It is estimated that there are TWO million workers in the United States employed in occupations at risk for the development of silicosis. These include miners, foundry workers, stonecutters, potters and ceramics workers, sandblasters, tunnel workers, and rock drillers. Silicosis is mostly found in adults over 40. It has four forms:

• Chronic. Chronic silicosis may take 15 or more years of exposure to develop. There is only mild impairment of lung functioning. Chronic silicosis may progress to more advanced forms.
• Complicated. Patients with complicated silicosis have noticeable shortness of breath, weight loss, and extensive formation of fibrous tissue (fibrosis) in the lungs. These patients are at risk for developing tuberculosis (TB).
• Accelerated. This form of silicosis appears after 5-10 years of intense exposure. The symptoms are similar to those of complicated silicosis. Patients in this group often develop rheumatoid arthritis and other autoimmune disorders.
• Acute. Acute silicosis develops within six months to two years of intense exposure to silica. The patient loses a great deal of weight and is constantly short of breath. These patients are at severe risk of TB.

Pulmonary Fibrosis

Definition

Pulmonary fibrosis is scarring in the lungs.

Description

Pulmonary fibrosis develops when the alveoli, tiny air sacs that transfer oxygen to the blood, become damaged and inflamed. The body tries to heal the damage with scars, but these scars collapse the alveoli and make the lungs less elastic. If the cycle of inflammation and scarring continues, the lungs become increasingly unable to deliver oxygen to the blood. Changes in the lungs can also increase the blood pressure in the pulmonary artery. This condition, called pulmonary hypertension, makes the heart work harder and it may fail.

Pulmonary fibrosis can result from many different lung diseases including sarcoidosis, drug reactions, autoimmune diseases, environmental allergies such as Farmer's lung, and exposure to toxic dusts and gases.

Pulmonary fibrosis that develops without a known cause is called idiopathic pulmonary fibrosis. This disease is equally common in men and women. It is usually diagnosed between the ages of 40 and 60.

Cystic fibrosis

Definition

Cystic fibrosis (CF) is an inherited disease that affects the lungs, digestive system, sweat glands, and male fertility. Its name derives from the fibrous scar tissue that develops in the pancreas, one of the principal organs affected by the disease.

Description

Cystic fibrosis affects the body's ability to move salt and water in and out of cells. This defect causes the lungs and pancreas to secrete abnormally thick mucus that blocks passageways and prevents proper function.
CF affects approximately 30,000 children and young adults in the United States and 70,000 people worldwide. Each year, about 1,000 babies are born with CF. CF primarily affects people of white northern-European descent (1 in 3,200). Rates are much lower in Hispanic (1 in 9,200), African-American (1 in 15,000) and Asian (1 in 31,000) populations.
Most children with CF are diagnosed by age two, and many symptoms of CF can be treated with drugs or nutritional supplements. Close attention to and prompt treatment of respiratory and digestive complications have dramatically increased the expected life span of a person with CF. While in the 1950s, children with CF rarely lived past age 6, today about half of all people with CF live past age 37, with the median life span expected to increase as treatments are improved.

Emphysema

Definition

Emphysema is a chronic respiratory disease where there is over-inflation of the air sacs (alveoli) in the lungs, causing a decrease in lung function, and often, breathlessness.

Description

Emphysema is the most common cause of death from respiratory disease in the United States, and is the fourth most common cause of death overall. There are 1.8 million Americans with the disease, which ranks fifteenth among chronic conditions that cause limitations of activity. The disease is usually caused by smoking, but a small number of cases are caused by an inherited defect.

Normally functioning lungs are elastic, efficiently expanding and recoiling as air passes freely through the bronchus to the alveoli, where oxygen is moved into the blood and carbon dioxide is filtered out. When a person inhales cigarette smoke or certain other irritants, his or her immune system responds by releasing substances that are meant to defend the lungs against the smoke. These substances can also attack the cells of the lungs, but the body normally inhibits such action with the release of other substances. In smokers and those with the inherited defect, however, no such prevention occurs and the lung tissue is damaged in such a way that it loses its elasticity. The small passageways (bronchioles) leading to the alveoli collapse, trapping air within the alveoli. The alveoli, unable to recoil efficiently and move the air out, over expand and rupture. As the disease progresses, coughing and shortness of breath occur. In the later stages, the lungs cannot supply enough oxygen to the blood. Emphysema often occurs with other respiratory diseases, particularly chronic bronchitis. These two diseases are often referred to as one disorder called chronic obstructive pulmonary disease (COPD).

Emphysema is most common among people aged 50 and older. Those with inherited emphysema may experience the onset as early as their thirties or forties. Men are more likely than women to develop emphysema, but female cases are increasing as the number of female smokers rises.

COPD

abbreviation for chronic obstructive pulmonary disease.

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chronic [kron´ik]

persisting for a long time; applied to a morbid state, designating one showing little change or extremely slow progression over a long period.

chronic airflow limitation (CAL) any pulmonary disorder occurring as a result of increased airway resistance or of decreased elastic recoil; the diseases most often associated are asthma, chronic bronchitis, and chronic pulmonary emphysema. Called also chronic obstructive pulmonary disease.

Chronic airflow limitation has the highest morbidity rate of any significant chronic pulmonary disorder in the United States and is the second most common cause of hospital admissions. It is difficult to estimate its exact incidence because most diseases of the respiratory tract are not reportable and there is some confusion in definition of terms related to diseases of this type. However, the Social Security Administration reports that CAL ranked only second to heart disease as the cause of disability in men over the age of 40. The incidence of CAL is increasing and, although not all specific causes are known, factors contributing to its development and affecting its degree of severity have been identified. Heavy cigarette smoking is probably the most important factor, and others are industrial pollution, occupational exposure to irritating inhalants, allergy, autoimmunity, genetic predisposition, and chronic infections.

Lung Cancer

Lung cancer

a pulmonary malignancy attributable in the majority of cases to cigarette smoking. Other predisposing factors are exposure to acronitrile, arsenic, asbestos, beryllium, chloromethyl ether, chromium, coal products, ionizing radiation, iron oxide, mustard gas, nickel, petroleum, uranium, and vinyl chloride. Lung cancer develops most often in scarred or chronically diseased lungs. It is usually far advanced when detected because metastases may precede detection of the primary lesion in the lung. Symptoms of lung cancer include persistent cough, hoarseness, dyspnea, purulent or blood-streaked sputum, chest pain, and repeated attacks of bronchitis or pneumonia. Diagnostic measures include x-ray films, fluoroscopy, tomography, bronchography, angiography, cytologic studies of sputum, bronchial washings or brushings, and needle biopsy. Epidermoid cancers and adenocarcinomas each account for approximately 30% of lung tumors; about 25% are small, or oat, cell carcinomas; and 15% are large cell anaplastic cancers. Small cell carcinomas frequently metastasize widely before diagnosis. Surgery is the most effective treatment, but only about 20% are resectable. Lung cancer is essentially incurable unless surgical resection can be accomplished. Thoracotomy is contraindicated if metastases are found in contralateral or scalene lymph nodes. Irradiation is used to treat localized lesions and unresectable intrathoracic tumors and as palliative therapy for metastatic lesions. Radiotherapy may also be administered after surgery to destroy remaining tumor cells and may be combined with chemotherapy. Targeted therapy with drugs such as paclitaxel, carboplatin, irinotecan, and erlotinib has also shown results. Chemotherapy is especially indicated for small cell carcinoma.

Pneumonia

Definition

Pneumonia is an infection of the lung that can be caused by nearly any class of organism known to cause human infections. These include bacteria, amoebae, viruses, fungi, and parasites. In the United States, pneumonia is the sixth most common disease leading to death; 2 million Americans develop pneumonia each year, and 40,000-70,000 die from it. Pneumonia is also the most common fatal infection acquired by already hospitalized patients. In developing countries, pneumonia ties with diarrhea as the most common cause of death. Even in nonfatal cases, pneumonia is a significant economic burden on the health care system. One study estimates that people in the American workforce who develop pneumonia cost employers five times as much in health care as the average worker.

According to the Centers for Disease Control and Prevention (CDC), however, the number of deaths from pneumonia in the United States has declined slightly since 2001.

Description

Anatomy of the lung

To better understand pneumonia, it is important to understand the basic anatomic features of the respiratory system. The human respiratory system begins at the nose and mouth, where air is breathed in (inspired) and out (expired). The air tube extending from the nose is called the nasopharynx. The tube carrying air breathed in through the mouth is called the oropharynx. The nasopharynx and the oropharynx merge into the larynx. The oropharynx also carries swallowed substances, including food, water, and salivary secretion, which must pass into the esophagus and then the stomach. The larynx is protected by a trap door called the epiglottis. The epiglottis prevents substances that have been swallowed, as well as substances that have been regurgitated (thrown up), from heading down into the larynx and toward the lungs.

A useful method of picturing the respiratory system is to imagine an upside-down tree. The larynx flows into the trachea, which is the tree trunk, and thus the broadest part of the respiratory tree. The trachea divides into two tree limbs, the right and left bronchi. Each one of these branches off into multiple smaller bronchi, which course through the tissue of the lung. Each bronchus divides into tubes of smaller and smaller diameter, finally ending in the terminal bronchioles. The air sacs of the lung, in which oxygen-carbon dioxide exchange actually takes place, are clustered at the ends of the bronchioles like the leaves of a tree. They are called alveoli.

The tissue of the lung which serves only a supportive role for the bronchi, bronchioles, and alveoli is called the lung stroma.

Bronchitis

Definition

[brongkī′tis]

Etymology: Gk, bronchos, windpipe, itis, inflammation

acute or chronic inflammation of the mucous membranes of the tracheobronchial tree. Caused by the spread of upper respiratory viral or sometimes bacterial infections to the bronchi, it is often observed with or after childhood infections, such as measles, whooping cough, diphtheria, and typhoid fever. 

Bronchitis is an inflammation of the air passages between the nose and the lungs, including the windpipe or trachea and the larger air tubes of the lung that bring air in from the trachea (bronchi). Bronchitis can either be of brief duration (acute) or have a long course (chronic). Acute bronchitis is usually caused by a viral infection, but can also be caused by a bacterial infection and can heal without complications. Chronic bronchitis is a sign of serious lung disease that may be slowed but cannot be cured.

Description

Although acute and chronic bronchitis are both inflammations of the air passages, their causes and treatments are different. Acute bronchitis is most prevalent in winter. It usually follows a viral infection, such as a cold or the flu, and can be accompanied by a secondary bacterial infection. Acute bronchitis resolves within two weeks, although the cough may persist longer. Acute bronchitis, like any upper airway inflammatory process, can increase a person's likelihood of developing pneumonia.

Anyone can get acute bronchitis, but infants, young children, and the elderly are more likely to get the disease because people in these age groups generally have weaker immune systems. Smokers and people with heart or other lung diseases are also at higher risk of developing acute bronchitis. Individuals exposed to chemical fumes or high levels of air pollution also have a greater chance of developing acute bronchitis.

Chronic bronchitis is a major cause of disability and death in the United States. The American Lung Association estimates that about 14 million Americans suffer from the disease. Like acute bronchitis, chronic bronchitis is an inflammation of airways accompanied by coughing and spitting up of phlegm. In chronic bronchitis, these symptoms are present for at least three months in each of two consecutive years.

Chronic bronchitis is caused by inhaling bronchial irritants, especially cigarette smoke. Until recently, more men than women developed chronic bronchitis, but as the number of women who smoke has increased, so has their rate of chronic bronchitis. Because this disease progresses slowly, middle-aged and older people are more likely to be diagnosed with chronic bronchitis.

Malarian

Definition

Malaria is a serious infectious disease spread by certain mosquitoes. It is most common in tropical climates. It is characterized by recurrent symptoms of chills, fever, and an enlarged spleen. The disease can be treated with medication, but it often recurs. Malaria is endemic (occurs frequently in a particular locality) in many third world countries. Isolated, small outbreaks sometimes occur within the boundaries of the United States.

Description

Malaria is a growing problem in the United States. Although only about 1400 new cases were reported in the United States and its territories in 2000, many involved returning travelers. In addition, locally transmitted malaria has occurred in California, Florida, Texas, Michigan, New Jersey, and New York City. While malaria can be transmitted in blood, the American blood supply is not screened for malaria. Widespread malarial epidemics are far less likely to occur in the United States, but small localized epidemics could return to the Western world. As of late 2002, primary care physicians are being advised to screen returning travelers with fever for malaria, and a team of public health doctors in Minnesota is recommending screening immigrants, refugees, and international adoptees for the disease—particularly those from high-risk areas.

The picture is far more bleak, however, outside the territorial boundaries of the United States. A recent government panel warned that disaster looms over Africa from the disease. Malaria infects between 300 and 500 million people every year in Africa, India, southeast Asia, the Middle East, Oceania, and Central and South America. A 2002 report stated that malaria kills 2.7 million people each year, more than 75 percent of them African children under the age of five. It is predicted that within five years, malaria will kill about as many people as does AIDS. As many as half a billion people worldwide are left with chronic anemia due to malaria infection. In some parts of Africa, people battle up to 40 or more separate episodes of malaria in their lifetimes. The spread of malaria is becoming even more serious as the parasites that cause malaria develop resistance to the drugs used to treat the condition. In late 2002, a group of public health researchers in Thailand reported that a combination treatment regimen involving two drugs known as dihydroartemisinin and azithromycin shows promise in treating multidrug-resistant malaria in southeast Asia.

Tuberculosis

 Key facts

• Tuberculosis (TB) is second only to HIV/AIDS as the greatest killer worldwide due to a single infectious agent.
• In 2010, 8.8 million people fell ill with TB and 1.4 million died from TB.
• Over 95% of TB deaths occur in low- and middle-income countries, and it is among the top three causes of death for women aged 15 to 44.
• In 2009, there were about 10 million orphan children as a result of TB deaths among parents.
• TB is a leading killer of people living with HIV causing one quarter of all deaths.
• Multi-drug resistant TB (MDR-TB) is present in virtually all countries surveyed.
• The estimated number of people falling ill with tuberculosis each year is declining, although very slowly, which means that the world is on track to achieve the Millennium Development Goal to reverse the spread of TB by 2015.
• The TB death rate dropped 40% between 1990 and 2010.

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TB is spread from person to person through the air. When people with lung TB cough, sneeze or spit, they propel the TB germs into the air. A person needs to inhale only a few of these germs to become infected.
About one-third of the world's population has latent TB, which means people have been infected by TB bacteria but are not (yet) ill with disease and cannot transmit the disease.
People infected with TB bacteria have a lifetime risk of falling ill with TB of 10%. However persons with compromised immune systems, such as people living with HIV, malnutrition or diabetes, or people who use tobacco, have a much higher risk of falling ill.
When a person develops active TB (disease), the symptoms (cough, fever, night sweats, weight loss etc.) may be mild for many months. This can lead to delays in seeking care, and results in transmission of the bacteria to others. People ill with TB can infect up to 10-15 other people through close contact over the course of a year. Without proper treatment up to two thirds of people ill with TB will die.