Bronchitis

Bronchitis is inflammation of the mucous membranes of the bronchi, the airways that carry airflow from
the trachea into the lungs. Bronchitis can be classified into two categories, acute and chronic, each of
which has unique etiologies, pathologies, and therapies.
Acute bronchitis is characterized by the development of a cough, with or without the production
of sputum, mucus that is expectorated(coughed up) from the respiratory tract. Acute bronchitis often
occurs during the course of an acute viral illness such as the common cold orinfluenza. Viruses cause
about 90% of cases of acute bronchitis, whereas bacteria account for less than 10%.[1]
Chronic bronchitis, a type of chronic obstructive pulmonary disease, is characterized by the presence of a
productive cough that lasts for 3 months or more per year for at least 2 years. Chronic bronchitis most
often develops due to recurrent injury to the airways caused by inhaled irritants. Cigarette smoking is the
most common cause, followed by air pollution and occupational exposure to irritants, and cold air.

Asthma
Asthma (from the Greek άσθμα, ásthma, "panting") is a common chronic inflammatory disease of
the airways characterized by variable and recurring symptoms, reversible airflow obstruction,
and bronchospasm.[1] Symptoms include wheezing, coughing, chest tightness, and shortness of breath.[2]
Treatment of acute symptoms is usually with an inhaled short-acting beta-2 agonist (such as salbutamol).
[3]
 Symptoms can be prevented by avoiding triggers, such as allergens[4] and irritants, and by
inhaling corticosteroids.[5] Leukotriene antagonists are less effective than corticosteroids and thus less
preferred.[6]
The prevalence of asthma has increased significantly since the 1970s. As of 2009, 300 million people
were affected worldwide.[7] In 2009 asthma caused 250,000 deaths globally.[7] Despite this, with proper
control of asthma with step down therapy, prognosis is generally good.

Emphysema
Emphysema is a long-term, progressive disease of the lungs that primarily causes shortness of breath. In
people with emphysema, the tissues necessary to support the physical shape and function of the lungs
are destroyed. It is included in a group of diseases called chronic obstructive pulmonary disease or COPD
(pulmonary refers to the lungs). Emphysema is called an obstructive lung disease because the
destruction of lung tissue around smaller sacs, called alveoli, makes these air sacs unable to hold their
functional shape upon exhalation. It is often caused by smoking.
The term means swelling and comes from the Greek ἐμφυσᾶν emhysan meaning inflate, itself composed
of ἐν en meaning in and φυσᾶνphysan meaning breath, blast.

Pneumonia
Pneumonia is an inflammatory condition of the lung.[1] It is often characterized as including inflammation
of the parenchyma of the lung (that is, the alveoli) and abnormal alveolar filling with fluid
(consolidation and exudation).[2]
The alveoli are microscopic air filled sacs in the lungs responsible for gas exchange. Pneumonia can
result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical
or physical injury to the lungs. Its cause may also be officially described as unknown when infectious
causes have been excluded.
Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in
breathing. Diagnostic tools include x-rays and examination of the sputum. Treatment depends on the
cause of pneumonia; bacterial pneumonia is treated with antibiotics.
Pneumonia is common, occurring in all age groups, and is a leading cause of death among the young, the
old, and the chronically ill.[3]Vaccines to prevent certain types of pneumonia are available.
The prognosis depends on the type of pneumonia, the treatment, any complications, and the person's
underlying health.

Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of
the family Orthomyxoviridae (the influenza viruses), that affects birds and mammals. The most common
symptoms of the disease are chills, fever, sore throat, muscle pains, severeheadache, coughing,
weakness/fatigue and general discomfort.[1] Although it is often confused with other influenza-like
illnesses, especially the common cold, influenza is a more severe disease than the common cold and is
caused by a different type of virus.[2] Influenza may produce nausea and vomiting, particularly in children,
[1]
 but these symptoms are more common in the unrelated gastroenteritis, which is sometimes called
"stomach flu" or "24-hour flu".[3]
Typically, influenza is transmitted through the air by coughs or sneezes, creating aerosols containing the
virus. Influenza can also be transmitted by direct contact with bird droppings or nasal secretions, or
through contact with contaminated surfaces. Airborne aerosols have been thought to cause most
infections, although which means of transmission is most important is not absolutely clear.[4] Influenza
viruses can be inactivated by sunlight, disinfectants and detergents.[5][6] As the virus can be inactivated by
soap, frequent hand washing reduces the risk of infection.[7][8][9][10]
Influenza spreads around the world in seasonal epidemics, resulting in the deaths of between 250,000
and 500,000 people every year,[11] up to millions in some pandemic years. On average 41,400 people
died each year in the United States between 1979 and 2001 from influenza.[12] In 2010 the CDC in
the United States changed the way it reports the 30 year estimates for deaths. Now they are reported as
a range from a low of about 3,300 deaths to a high of 49,000 per year.[13]
Three influenza pandemics occurred in the 20th century and killed tens of millions of people, with each of
these pandemics being caused by the appearance of a new strain of the virus in humans. Often, these
new strains appear when an existing flu virus spreads to humans from other animal species, or when an
existing human strain picks up new genes from a virus that usually infects birds or pigs. An avian strain
named H5N1 raised the concern of a new influenza pandemic, after it emerged in Asia in the 1990s, but it
has not evolved to a form that spreads easily between people.[14] In April 2009 a novel flu strain evolved
that combined genes from human, pig, and bird flu, initially dubbed "swine flu" and also known
as influenza A/H1N1, emerged in Mexico, the United States, and several other nations. The World Health
Organization officially declared the outbreak to be a pandemic on June 11, 2009 (see 2009 flu pandemic).
The WHO's declaration of a pandemic level 6 was an indication of spread, not severity, the strain actually
having a lower mortality rate than common flu outbreaks.[15]
Vaccinations against influenza are usually given to people in developed countries[16] and to farmed
poultry.[17] The most common human vaccine is the trivalent influenza vaccine (TIV) that contains purified
and inactivated material from three viral strains. Typically, this vaccine includes material from
two influenza A virus subtypes and one influenza B virus strain.[18] The TIV carries no risk of transmitting
the disease, and it has very low reactivity. A vaccine formulated for one year may be ineffective in the
following year, since the influenza virus evolves rapidly, and new strains quickly replace the older
ones. Antiviral drugs can be used to treat influenza, with neuraminidase inhibitors being particularly
effective.

Tuberculosis
Tuberculosis or TB (short for tubercles  bacillus) is a common and often deadly infectious
disease caused by various strains ofmycobacteria, usually Mycobacterium tuberculosis in humans.
[1]
 Tuberculosis usually attacks the lungs but can also affect other parts of the body. It is spread through
the air when people who have the disease cough, sneeze, or spit.[2] Most infections in humans result in
anasymptomatic, latent infection, and about one in ten latent infections eventually progresses to active
disease, which, if left untreated, kills more than 50% of its victims.
The classic symptoms are a chronic cough with blood-tinged sputum, fever, night sweats, and weight
loss (the last giving rise to the formerly prevalent colloquial term "consumption"). Infection of other organs
causes a wide range of symptoms. Diagnosis relies on radiology(commonly chest X-rays), a tuberculin
skin test, blood tests, as well as microscopic examination and microbiological culture of bodily
fluids.Treatment is difficult and requires long courses of multiple antibiotics. Contacts are also screened
and treated if necessary. Antibiotic resistance is a growing problem in (extensively) multi-drug-resistant
tuberculosis. Prevention relies on screening programs and vaccination, usually with Bacillus Calmette-
Guérin vaccine.
One third of the world's population is thought to be infected with M. tuberculosis,[3][4] and new infections
occur at a rate of about one per second.[5] The proportion of people who become sick with tuberculosis
each year is stable or falling worldwide but, because of population growth, the absolute number of new
cases is still increasing.[5] In 2007 there were an estimated 13.7 million chronic active cases, 9.3 million
new cases, and 1.8 million deaths, mostly in developing countries.[6] In addition, more people in
the developed world are contracting tuberculosis because their immune systems are compromised
by immunosuppressive drugs, substance abuse, or AIDS. The distribution of tuberculosis is not uniform
across the globe; about 80% of the population in many Asian and African countries test positive in
tuberculin tests, while only 5-10% of the US population test positive.[1]

Lung cancer
Lung cancer is a disease which consists of uncontrolled cell growth in tissues of the lung. This growth
may lead to metastasis, which is the invasion of adjacent tissue and infiltration beyond the lungs. The vast
majority of primary lung cancers are carcinomas of the lung, derived from epithelial cells. Lung cancer,
the most common cause of cancer-related death in men and women, is responsible for 1.3 million
deathsworldwide annually, as of 2004.[1] The most common symptoms are shortness of breath, coughing
(including coughing up blood), and weight loss.[2]
The main types of lung cancer are small cell lung carcinoma and non-small cell lung carcinoma. This
distinction is important, because the treatment varies; non-small cell lung carcinoma (NSCLC) is
sometimes treated with surgery, while small cell lung carcinoma (SCLC) usually responds better
to chemotherapy and radiation.[3] The most common cause of lung cancer is long-term exposure
to tobacco smoke.[4] The occurrence of lung cancer in nonsmokers, who account for as many as 15% of
cases,[5] is often attributed to a combination of genetic factors,[6][7] radon gas,[8] asbestos,[9] and air
pollution[10][11][12] including secondhand smoke.[13][14]
Lung cancer may be seen on chest radiograph and computed tomography (CT scan). The diagnosis is
confirmed with a biopsy. This is usually performed by bronchoscopy or CT-guided biopsy. Treatment
and prognosis depend upon the histological type of cancer, the stage(degree of spread), and the
patient's performance status. Possible treatments include surgery, chemotherapy, and radiotherapy.
Survival varies, depending on stage, overall health, and other factors, but the overall five-year survival
rate for all persons diagnosed with lung cancer is 14%.[2]