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Pneumonia

2007 Schools Wikipedia Selection. Related subjects: Health and medicine

   CAPTION: Pneumonia
   Classifications and external resources

    ICD- 10   J 12., J 13., J 14., J 15., J 16., J 17., J 18., P 23.
     ICD- 9   480- 486, 770.0
   DiseasesDB 10166
   eMedicine  topic list
   MeSH       C08.381.677

   Pneumonia is an illness of the lungs and respiratory system in which
   the alveoli (microscopic air-filled sacs of the lung responsible for
   absorbing oxygen from the atmosphere) become inflamed and flooded with
   fluid. Pneumonia can result from a variety of causes, including
   infection with bacteria, viruses, fungi, or parasites. Pneumonia may
   also occur from chemical or physical injury to the lungs, or indirectly
   due to another medical illness, such as lung cancer or alcohol abuse.

   Typical symptoms associated with pneumonia include cough, chest pain,
   fever, and difficulty 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 a common illness, occurs in all age groups, and is a
   leading cause of death among the elderly and people who are chronically
   ill. Vaccines to prevent certain types of pneumonia are available. The
   prognosis for an individual depends on the type of pneumonia, the
   appropriate treatment, any complications, and the person's underlying
   health.

Symptoms

   Pneumonia fills the lung's alveoli with fluid, keeping oxygen from
   reaching the bloodstream. The alveolus on the left is normal, while the
   alveolus on the right is full of fluid from pneumonia.
   Enlarge
   Pneumonia fills the lung's alveoli with fluid, keeping oxygen from
   reaching the bloodstream. The alveolus on the left is normal, while the
   alveolus on the right is full of fluid from pneumonia.

   People with infectious pneumonia often have a cough that produces
   greenish or yellow sputum and a high fever that may be accompanied by
   shaking chills. Shortness of breath is also common, as is pleuritic
   chest pain, a sharp or stabbing pain, either felt or worse during deep
   breaths or coughs. People with pneumonia may cough up blood, experience
   headaches, or develop sweaty and clammy skin. Other symptoms may
   include loss of appetite, fatigue, blueness of the skin, nausea,
   vomiting, and joint pains or muscle aches. Less common forms of
   pneumonia can cause a variety of other symptoms. For instance,
   pneumonia caused by Legionella may cause abdominal pain and diarrhea,
   while pneumonia caused by tuberculosis or Pneumocystis may cause only
   weight loss and night sweats. In elderly people the manifestations of
   pneumonia may not be typical. Instead, they may develop new or
   worsening confusion or may experience unsteadiness leading to falls.
   Infants with pneumonia may have many of the symptoms above, but in many
   cases, they are simply sleepy or have decreased appetite.

Diagnosis

   To diagnose pneumonia, health care providers rely on a patient's
   symptoms and findings from physical examination. Information from a
   chest X-ray, blood tests, and sputum cultures may also be helpful. The
   chest X-ray is typically used for diagnosis in hospitals and some
   clinics with X-ray facilities. However, in a community setting (
   general practice), pneumonia is usually diagnosed based on symptoms and
   physical examination alone. Diagnosing pneumonia can be difficult in
   some people, especially those who have other illnesses. Occasionally a
   chest CT scan or other tests may be needed to distinguish pneumonia
   from other illnesses.

Physical examination

   Individuals with symptoms of pneumonia need medical evaluation.
   Physical examination by a health care provider may reveal fever or
   sometimes low body temperature, an increased respiratory rate, low
   blood pressure, a fast heart rate, or a low oxygen saturation, which is
   the amount of oxygen in the blood as indicated by either pulse oximetry
   or blood gas analysis. People who are struggling to breathe, confused,
   or who have cyanosis (blue-tinged skin) require immediate attention.
   Pneumonia as seen on chest x-ray. A: Normal chest x-ray. B: Abnormal
   chest x-ray with shadowing from pneumonia in the right lung (left side
   of image).
   Enlarge
   Pneumonia as seen on chest x-ray. A: Normal chest x-ray. B: Abnormal
   chest x-ray with shadowing from pneumonia in the right lung (left side
   of image).

   Listening to the lungs with a stethoscope ( auscultation) can reveal
   several things. A lack of normal breath sounds, the presence of
   crackling sounds ( rales), or increased loudness of whispered speech
   (whispered pectoriloquy) can identify areas of the lung that are stiff
   and full of fluid, called "consolidation." The examiner may also feel
   the way the chest expands ( palpation) and tap the chest wall (
   percussion) to further localize consolidation. The examiner may also
   palpate for increased vibration of the chest when speaking (tactile
   fremitus).

Chest X-rays, sputum cultures and other tests

   An important test for detecting pneumonia in unclear situations is a
   chest x-ray. Chest x-rays can reveal areas of opacity (seen as white)
   which represent consolidation. Pneumonia is not always seen on x-rays,
   either because the disease is only in its initial stages, or because it
   involves a part of the lung not easily seen by x-ray. In some cases,
   chest CT ( computed tomography) can reveal pneumonia that is not seen
   on chest x-ray. X-rays can be misleading, because other problems, like
   lung scarring and congestive heart failure, can mimic pneumonia on
   x-ray. Chest x-rays are also used to evaluate for complications of
   pneumonia. ( See below.)

   If an individual is not getting better with antibiotics, or if the
   health care provider has concerns about the diagnosis, a culture of the
   person's sputum may be requested. Sputum cultures generally take at
   least two to three days, so they are mainly used to confirm that the
   infection is sensitive to an antibiotic that has already been started.
   A blood sample may similarly be cultured to look for infection in the
   blood ( blood culture). Any bacteria identified are then tested to see
   which antibiotics will be most effective.

   A complete blood count may show a high white blood cell count,
   indicating the presence of an infection or inflammation. In some people
   with immune system problems, the white blood cell count may appear
   deceptively normal. Blood tests may be used to evaluate kidney function
   (important when prescribing certain antibiotics) or to look for low
   blood sodium. Low blood sodium in pneumonia is thought to be due to
   extra anti-diuretic hormone produced when the lungs are diseased (
   SIADH). Specific blood serology tests for other bacteria (Mycoplasma,
   Legionella and Chlamydophila) and a urine test for Legionella antigen
   are available. Respiratory secretions can also be tested for the
   presence of viruses such as influenza, respiratory syncytial virus, and
   adenovirus.

Pathophysiology

   Upper panel shows a normal lung under a microscope. The white spaces
   are alveoli that contain air. Lower panel shows a lung with pneumonia
   under a microscope. The alveoli are filled with inflammation and
   debris.
   Enlarge
   Upper panel shows a normal lung under a microscope. The white spaces
   are alveoli that contain air. Lower panel shows a lung with pneumonia
   under a microscope. The alveoli are filled with inflammation and
   debris.

   The symptoms of infectious pneumonia are caused by the invasion of the
   lungs by microorganisms and by the immune system's response to the
   infection. Although over one hundred strains of microorganism can cause
   pneumonia, only a few of them are responsible for most cases. The most
   common causes of pneumonia are viruses and bacteria. Less common causes
   of infectious pneumonia include fungi and parasites.

Viruses

   Viruses must invade cells in order to reproduce. Typically, a virus
   reaches the lungs when airborne droplets are inhaled through the mouth
   and nose. Once in the lungs, the virus invades the cells lining the
   airways and alveoli. This invasion often leads to cell death, either
   when the virus directly kills the cells, or through a type of cell
   self-destruction called apoptosis. When the immune system responds to
   the viral infection, even more lung damage occurs. White blood cells,
   mainly lymphocytes, activate a variety of chemical cytokines which
   allow fluid to leak into the alveoli. This combination of cell
   destruction and fluid-filled alveoli interrupts the normal
   transportation of oxygen into the bloodstream.

   In addition to damaging the lungs, many viruses affect other organs and
   thus can disrupt many different body functions. Viruses also can make
   the body more susceptible to bacterial infections; for this reason,
   bacterial pneumonia often complicates viral pneumonia.

   Viral pneumonia is commonly caused by viruses such as influenza virus,
   respiratory syncytial virus (RSV), adenovirus, and metapneumovirus.
   Herpes simplex virus is a rare cause of pneumonia except in newborns.
   People with immune system problems are also at risk for pneumonia
   caused by cytomegalovirus (CMV).

Bacteria

   Bacteria typically enter the lung when airborne droplets are inhaled,
   but they can also reach the lung through the bloodstream when there is
   an infection in another part of the body. Many bacteria live in parts
   of the upper respiratory tract, such as the nose, mouth and sinuses,
   and can easily be inhaled into the alveoli. Once inside the alveoli,
   bacteria may invade the spaces between cells and between alveoli
   through connecting pores. This invasion triggers the immune system to
   send neutrophils, which are a type of defensive white blood cell, to
   the lungs. The neutrophils engulf and kill the offending organisms, and
   they also release cytokines, causing a general activation of the immune
   system. This leads to the fever, chills, and fatigue common in
   bacterial and fungal pneumonia. The neutrophils, bacteria, and fluid
   from surrounding blood vessels fill the alveoli and interrupt normal
   oxygen transportation.
   The bacterium Streptococcus pneumoniae, a common cause of pneumonia,
   photographed through an electron microscope.
   Enlarge
   The bacterium Streptococcus pneumoniae, a common cause of pneumonia,
   photographed through an electron microscope.

   Bacteria often travel from an infected lung into the bloodstream,
   causing serious or even fatal illness such as septic shock, with low
   blood pressure and damage to multiple parts of the body including the
   brain, kidneys, and heart. Bacteria can also travel to the area between
   the lungs and the chest wall (the pleural cavity) causing a
   complication called an empyema.

   The most common causes of bacterial pneumonia are Streptococcus
   pneumoniae, Gram-negative bacteria and "atypical" bacteria. The terms
   "Gram-positive" and "Gram-negative" refer to the bacteria's colour
   (purple or red, respectively) when stained using a process called the
   Gram stain. The term "atypical" is used because atypical bacteria
   commonly affect healthier people, cause generally less severe
   pneumonia, and respond to different antibiotics than other bacteria.

   The types of Gram-positive bacteria that cause pneumonia can be found
   in the nose or mouth of many healthy people. Streptococcus pneumoniae,
   often called "pneumococcus", is the most common bacterial cause of
   pneumonia in all age groups except newborn infants. Another important
   Gram-positive cause of pneumonia is Staphylococcus aureus.
   Gram-negative bacteria cause pneumonia less frequently than
   gram-positive bacteria. Some of the gram-negative bacteria that cause
   pneumonia include Haemophilus influenzae, Klebsiella pneumoniae,
   Escherichia coli, Pseudomonas aeruginosa and Moraxella catarrhalis.
   These bacteria often live in the stomach or intestines and may enter
   the lungs if vomit is inhaled. "Atypical" bacteria which cause
   pneumonia include Chlamydophila pneumoniae, Mycoplasma pneumoniae, and
   Legionella pneumophila.

Fungi

   Fungal pneumonia is uncommon, but it may occur in individuals with
   immune system problems due to AIDS, immunosuppresive drugs, or other
   medical problems. The pathophysiology of pneumonia caused by fungi is
   similar to that of bacterial pneumonia. Fungal pneumonia is most often
   caused by Histoplasma capsulatum, Cryptococcus neoformans, Pneumocystis
   jiroveci, and Coccidioides immitis. Histoplasmosis is most common in
   the Mississippi River basin, and coccidioidomycosis is most common in
   the southwestern United States.

Parasites

   A variety of parasites can affect the lungs. These parasites typically
   enter the body through the skin or by being swallowed. Once inside the
   body, they travel to the lungs, usually through the blood. There, as in
   other types of pneumonia, a combination of cellular destruction and
   immune response causes disruption of oxygen transportation. One type of
   white blood cell, the eosinophil, responds vigorously to parasite
   infection. Eosinophils in the lungs can lead to eosinophilic pneumonia,
   thus complicating the underlying parasitic pneumonia. The most common
   parasites causing pneumonia are Toxoplasma gondii, Strongyloides
   stercoralis, and Ascariasis.

Types of pneumonia

   Pneumonias can be classified in several different ways. Pathologists
   classified them according to the anatomic changes that were found in
   the lungs during autopsies. As more became known about the
   microorganisms causing pneumonia, a microbiologic classification arose,
   and with the advent of x-rays, a radiological classification was
   developed. Another important classification system used for pneumonia
   is the combined clinical classification, which combines many factors,
   including age, risk factors for certain microorganisms, the presence of
   underlying lung disease and underlying systemic disease, and whether he
   or she has recently been hospitalized.

Early classification schemes

   Initial descriptions of pneumonia focused on the anatomic or pathologic
   appearance of the lung, either by direct inspection at autopsy or by
   its appearance under a microscope. A lobar pneumonia is an infection
   that only involves a single lobe, or section, of a lung. Lobar
   pneumonia is often due to Streptococcus pneumoniae. Multilobar
   pneumonia involves more than one lobe, and it often is a more severe
   illness than lobar pneumonia. Interstitial pneumonia involves the areas
   in between the alveoli, and it may be called "interstitial
   pneumonitis." Interstitial pneumonia is more likely to be caused by
   viruses or by atypical bacteria.

   The discovery of x-rays made it possible to determine the anatomic type
   of pneumonia without direct examination of the lungs at autopsy and led
   to the development of a radiological classification. Early
   investigators distinguished between typical lobar pneumonia and
   atypical (e.g. Chlamydophila) or viral pneumonia using the location,
   distribution, and appearance of the opacities they saw on chest x-rays.
   Certain x-ray findings can be used to help predict the course of
   illness, although it is not possible to clearly determine the
   microbiologic cause of a pneumonia based on x-rays alone.

   With the advent of modern microbiology, classification based upon the
   causative microorganism became possible. Determining which
   microorganism is causing an individual's pneumonia is an important step
   in deciding treatment type and length. Sputum cultures, blood cultures,
   tests on respiratory secretions, and specific blood tests are used to
   determine the microbiologic classification. Because such laboratory
   testing typically takes several days, microbiologic classification is
   usually not possible at the time of initial diagnosis.

Combined clinical classification

   Traditionally, clinicians have classified pneumonia by clinical
   characteristics, dividing them into "acute" (less than three weeks
   duration) and "chronic" pneumonias. This is useful because chronic
   pneumonias tend to be either non-infectious, or mycobacterial, fungal,
   or mixed bacterial infections caused by airway obstruction. Acute
   pneumonias are further divided into the classic bacterial
   bronchopneumonias (such as Streptococcus pneumoniae), the atypical
   pneumonias (such as the interstitial pneumonitis of Mycoplasma
   pneumoniae or Chlamydia pneumoniae), and the aspiration pneumonia
   syndromes.

   The combined clinical classification, now the most commonly used
   classification scheme, attempts to identify a person's risk factors
   when he or she first comes to medical attention. The advantage of this
   classification scheme over previous systems is that it can help guide
   the selection of appropriate initial treatments even before the
   microbiologic cause of the pneumonia is known. There are two broad
   categories of pneumonia in this scheme: Community-acquired pneumonia
   and hospital-acquired pneumonia.

Community-acquired pneumonia

   Community-acquired pneumonia (CAP) is infectious pneumonia in a person
   who has not recently been hospitalized. CAP is the most common type of
   pneumonia. The most common causes of CAP differ depending on a person's
   age, but they include Streptococcus pneumoniae, viruses, the atypical
   bacteria, and Haemophilus influenzae. Overall, Streptococcus pneumoniae
   is the most common cause of community-acquired pneumonia worldwide.
   Gram-negative bacteria cause CAP in certain at-risk populations. CAP is
   the fourth most common cause of death in the United Kingdom and the
   sixth in the United States. An outdated term, walking pneumonia, has
   been used to describe a type of community-acquired pneumonia of less
   severity (hence the fact that the patient can continue to "walk" rather
   than require hospitalization). Walking pneumonia is usually caused by a
   virus or by atypical bacteria.

Hospital-acquired pneumonia

   Hospital-acquired pneumonia, also called nosocomial pneumonia, is
   pneumonia acquired during or after hospitalization for another illness
   or procedure. The causes, microbiology, treatment and prognosis are
   different from those of community-acquired pneumonia. Up to 5% of
   patients admitted to a hospital for other causes subsequently develop
   pneumonia. Hospitalized patients may have many risk factors for
   pneumonia, including mechanical ventilation, prolonged malnutrition,
   underlying heart and lung diseases, decreased amounts of stomach acid,
   and immune disturbances. Additionally, the microorganisms a person is
   exposed to in a hospital are often different from those at home.
   Hospital-acquired microorganisms may include resistant bacteria such as
   MRSA, Pseudomonas, Enterobacter, and Serratia. Because individuals with
   hospital-acquired pneumonia usually have underlying illnesses and are
   exposed to more dangerous bacteria, it tends to be more deadly than
   community-acquired pneumonia. Ventilator-associated pneumonia (VAP) is
   a subset of hospital-acquired pneumonia. VAP is pneumonia which occurs
   after at least 48 hours of intubation and mechanical ventilation.

Other types of pneumonia

     * Severe acute respiratory syndrome (SARS)

          SARS is a highly contagious and deadly type of pneumonia which
          first occurred in 2002 after initial outbreaks in China. SARS is
          caused by the SARS coronavirus, a previously unknown pathogen.
          New cases of SARS have not been seen since June 2003.

     * Bronchiolitis obliterans organizing pneumonia (BOOP)

          BOOP is caused by inflammation of the small airways of the
          lungs. It is also known as cryptogenic organizing pneumonitis
          (COP).

     * Eosinophilic pneumonia

          Eosinophilic pneumonia is invasion of the lung by eosinophils, a
          particular kind of white blood cell. Eosinophilic pneumonia
          often occurs in response to infection with a parasite or after
          exposure to certain types of environmental factors.

     * Chemical pneumonia

          Chemical pneumonia (usually called chemical pneumonitis) is
          caused by chemical toxins such as pesticides, which may enter
          the body by inhalation or by skin contact. When the toxic
          substance is an oil, the pneumonia may be called lipoid
          pneumonia.

     * Aspiration pneumonia

          Aspiration pneumonia (or aspiration pneumonitis) is caused by
          aspirating oral or gastric contents, either while eating, or
          after reflux or vomiting. The resulting lung inflammation is not
          an infection but can contribute to one, since the material
          aspirated may contain anaerobic bacteria or other unusual causes
          of pneumonia. Aspiration is a leading cause of death among
          hospital and nursing home patients, since they often cannot
          adequately protect their airways and may have otherwise impaired
          defenses.

Treatment

   Oral medication
   Enlarge
   Oral medication

   Most cases of pneumonia can be treated without hospitalization.
   Typically, oral antibiotics, rest, fluids, and home care are sufficient
   for complete resolution. However, people with pneumonia who are having
   trouble breathing, people with other medical problems, and the elderly
   may need more advanced treatment. If the symptoms get worse, the
   pneumonia does not improve with home treatment, or complications occur,
   the person will often have to be hospitalized.

   Antibiotics are used to treat bacterial pneumonia. In contrast,
   antibiotics are not useful for viral pneumonia, although they sometimes
   are used to treat or prevent bacterial infections that can occur in
   lungs damaged by a viral pneumonia. The antibiotic choice depends on
   the nature of the pneumonia, the most common microorganisms causing
   pneumonia in the local geographic area, and the immune status and
   underlying health of the individual. Treatment for pneumonia should
   ideally be based on the causative microorganism and its known
   antibiotic sensitivity. However, a specific cause for pneumonia is
   identified in only 50% of people, even after extensive evaluation.
   Because treatment should generally not be delayed in any person with a
   serious pneumonia, empiric treatment is usually started well before
   laboratory reports are available. In the United Kingdom, amoxicillin is
   the antibiotic selected for most patients with community-acquired
   pneumonia, sometimes with added clarithromycin; patients allergic to
   penicillins are given erythromycin instead of amoxicillin. In North
   America, where the "atypical" forms of community-acquired pneumonia are
   becoming more common, azithromycin, clarithromycin, and the
   fluoroquinolones have displaced amoxicillin as first-line treatment.
   The duration of treatment has traditionally been seven to ten days, but
   there is increasing evidence that shorter courses (as short as three
   days) are sufficient.

   Antibiotics for hospital-acquired pneumonia include vancomycin, third-
   and fourth-generation cephalosporins, carbapenems, fluoroquinolones,
   and aminoglycosides. These antibiotics are usually given intravenously.
   Multiple antibiotics may be administered in combination in an attempt
   to treat all of the possible causative microorganisms. Antibiotic
   choices vary from hospital to hospital because of regional differences
   in the most likely microorganisms, and because of differences in the
   microorganisms' abilities to resist various antibiotic treatments.

   People who have difficulty breathing due to pneumonia may require extra
   oxygen. Extremely sick individuals may require intensive care
   treatment, often including intubation and artificial ventilation.

   Viral pneumonia caused by influenza A may be treated with rimantadine
   or amantadine, while viral pneumonia caused by influenza A or B may be
   treated with oseltamivir or zanamivir. These treatments are beneficial
   only if they are started within 48 hours of the onset of symptoms. Many
   strains of H5N1 influenza A, also known as avian influenza or "bird
   flu," have shown resistance to rimantadine and amantadine. There are no
   known effective treatments for viral pneumonias caused by the SARS
   coronavirus, adenovirus, hantavirus, or parainfluenza virus.

Complications

   Sometimes pneumonia can lead to additional medical problems called
   complications. Complications are more frequently associated with
   bacterial pneumonia than with viral pneumonia. The most important
   complications include:

Respiratory and circulatory failure

   Because pneumonia affects the lungs, often people with pneumonia have
   difficulty breathing, and it may not be possible for them to breathe
   well enough to stay alive without support. Non-invasive breathing
   assistance may be helpful, such as with a bilevel positive airway
   pressure machine. In other cases, placement of an endotracheal tube
   (breathing tube) may be necessary, and a ventilator may be used to help
   the person breathe.

   Pneumonia can also cause respiratory failure by triggering acute
   respiratory distress syndrome (ARDS), which results from a combination
   of infection and inflammatory response. The lungs quickly fill with
   fluid and become very stiff. This stiffness, combined with severe
   difficulties extracting oxygen due to the alveolar fluid, create a need
   for mechanical ventilation.
   Pleural effusion. Chest x-ray showing a pleural effusion. The A arrow
   indicates "fluid layering" in the right chest. The B arrow indicates
   the width of the right lung. The volume of useful lung is reduced
   because of the collection of fluid around the lung.
   Enlarge
   Pleural effusion. Chest x-ray showing a pleural effusion. The A arrow
   indicates "fluid layering" in the right chest. The B arrow indicates
   the width of the right lung. The volume of useful lung is reduced
   because of the collection of fluid around the lung.

   Sepsis and septic shock are potential complications of pneumonia.
   Sepsis occurs when microorganisms enter the bloodstream and the immune
   system responds by secreting cytokines. Sepsis most often occurs with
   bacterial pneumonia; Streptococcus pneumoniae is the most common cause.
   Individuals with sepsis or septic shock need hospitalization in an
   intensive care unit. They often require intravenous fluids and
   medications to help keep their blood pressure from dropping too low.
   Sepsis can cause liver, kidney, and heart damage, among other problems,
   and it often causes death.

Pleural effusion, empyema and abscess

   Occasionally, microorganisms infecting the lung will cause fluid (a
   pleural effusion) to build up in the space that surrounds the lung (the
   pleural cavity). If the microorganisms themselves are present in the
   pleural cavity, the fluid collection is called an empyema. When pleural
   fluid is present in a person with pneumonia, the fluid can often be
   collected with a needle ( thoracentesis) and examined. Depending on the
   results of this examination, complete drainage of the fluid may be
   necessary, often requiring a chest tube. In severe cases of empyema,
   surgery may be needed. If the fluid is not drained, the infection may
   persist, because antibiotics do not penetrate well into the pleural
   cavity.

   Rarely, bacteria in the lung will form a pocket of infected fluid
   called an abscess. Lung abscesses can usually be seen with a chest
   x-ray or chest CT scan. Abscesses typically occur in aspiration
   pneumonia and often contain several types of bacteria. Antibiotics are
   usually adequate to treat a lung abscess, but sometimes the abscess
   must be drained by a surgeon or radiologist.

Prognosis and mortality

   With treatment, most types of bacterial pneumonia can be cured within
   one to two weeks. Viral pneumonia may last longer, and mycoplasmal
   pneumonia may take four to six weeks to resolve completely. The
   eventual outcome of an episode of pneumonia depends on how ill the
   person is when he or she is first diagnosed. One way to predict outcome
   is to use the Pneumonia Severity Score or CURB-65 score, which takes
   into account the severity of symptoms, any underlying diseases, and
   age. This score can be helpful in deciding whether or not to
   hospitalize the person.

   In the United States, about one of every twenty people with
   pneumococcal pneumonia will die. In cases where the pneumonia
   progresses to blood poisoning ( bacteremia), one of every five will
   die. The death rate (or mortality) also depends on the underlying cause
   of the pneumonia. Pneumonia caused by Mycoplasma, for instance, is
   associated with little mortality. However, about half of the people who
   develop methicillin-resistant Staphylococcus aureus ( MRSA) pneumonia
   while on a ventilator will die. In regions of the world without
   advanced health care systems, pneumonia is even deadlier. Limited
   access to clinics and hospitals, limited access to x-rays, limited
   antibiotic choices, and inability to treat underlying conditions
   inevitably leads to higher rates of death from pneumonia.

Prevention

   There are several ways to prevent infectious pneumonia. Appropriately
   treating underlying illnesses (such as AIDS) can decrease a person's
   risk of pneumonia. Smoking cessation is important not only because it
   helps to limit lung damage, but also because cigarette smoke interferes
   with many of the body's natural defenses against pneumonia.

   Research shows that there are several ways to prevent pneumonia in
   newborn infants. Testing pregnant women for Group B Streptococcus and
   Chlamydia trachomatis, and then giving antibiotic treatment if needed,
   reduces pneumonia in infants. Suctioning the mouth and throat of
   infants with meconium-stained amniotic fluid decreases the rate of
   aspiration pneumonia.

   Vaccination is important for preventing pneumonia in both children and
   adults. Vaccinations against Haemophilus influenzae and Streptococcus
   pneumoniae in the first year of life have greatly reduced their role in
   pneumonia in children. Vaccinating children against Streptococcus
   pneumoniae has also led to a decreased incidence of these infections in
   adults because many adults acquire infections from children. A vaccine
   against Streptococcus pneumoniae is also available for adults. In the
   U.S., it is currently recommended for all healthy individuals older
   than 65 and any adults with emphysema, congestive heart failure,
   diabetes mellitus, cirrhosis of the liver, alcoholism, cerebrospinal
   fluid leaks, or those who do not have a spleen. A repeat vaccination
   may also be required after five or ten years.

   Influenza vaccines should be given yearly to the same individuals who
   receive vaccination against Streptococcus pneumoniae. In addition,
   health care workers, nursing home residents, and pregnant women should
   receive the vaccine. When an influenza outbreak is occurring,
   medications such as amantadine, rimantadine, zanamivir, and oseltamivir
   can help prevent influenza.^,

Epidemiology

   Pneumonia is a common illness in all parts of the world. It is a major
   cause of death among all age groups. In children, the majority of
   deaths occur in the newborn period, with over two million deaths a year
   worldwide. The World Health Organization estimates that one in three
   newborn infant deaths are due to pneumonia. Mortality from pneumonia
   generally decreases with age until late adulthood. Elderly individuals,
   however, are at particular risk for pneumonia and associated mortality.

   More cases of pneumonia occur during the winter months than during
   other times of the year. Pneumonia occurs more commonly in males than
   females, and more often in Blacks than Caucasians. Individuals with
   underlying illnesses such as Alzheimer's disease, cystic fibrosis,
   emphysema, tobacco smoking, alcoholism, or immune system problems are
   at increased risk for pneumonia. These individuals are also more likely
   to have repeated episodes of pneumonia. People who are hospitalized for
   any reason are also at high risk for pneumonia.

History

   Hippocrates, the ancient Greek physician known as the "father of
   medicine."
   Enlarge
   Hippocrates, the ancient Greek physician known as the "father of
   medicine."

   The symptoms of pneumonia were described by Hippocrates (c. 460 BC–380
   BC):

     Peripneumonia, and pleuritic affections, are to be thus observed: If
     the fever be acute, and if there be pains on either side, or in
     both, and if expiration be if cough be present, and the sputa
     expectorated be of a blond or livid colour, or likewise thin,
     frothy, and florid, or having any other character different from the
     common... When pneumonia is at its height, the case is beyond remedy
     if he is not purged, and it is bad if he has dyspnoea, and urine
     that is thin and acrid, and if sweats come out about the neck and
     head, for such sweats are bad, as proceeding from the suffocation,
     rales, and the violence of the disease which is obtaining the upper
     hand.

   However, Hippocrates himself referred to pneumonia as a disease "named
   by the ancients." He also reported the results of surgical drainage of
   empyemas. Maimonides (1138-1204 AD) observed "The basic symptoms which
   occur in pneumonia and which are never lacking are as follows: acute
   fever, sticking [pleuritic] pain in the side, short rapid breaths,
   serrated pulse and cough." This clinical description is quite similar
   to those found in modern textbooks, and it reflected the extent of
   medical knowledge through the Middle Ages into the 19th century.

   Bacteria were first seen in the airways of individuals who died from
   pneumonia by Edwin Klebs in 1875. Initial work identifying the two
   common bacterial causes Streptococcus pneumoniae and Klebsiella
   pneumoniae was performed by Carl Friedländer and Albert Fränkel in 1882
   and 1884, respectively. Friedländer's initial work introduced the Gram
   stain, a fundamental laboratory test still used to identify and
   categorize bacteria. Christian Gram's paper describing the procedure in
   1884 helped differentiate the two different bacteria and showed that
   pneumonia could be caused by more than one microorganism.

   Sir William Osler, known as "the father of modern medicine,"
   appreciated the morbidity and mortality of pneumonia, describing it as
   the "captain of the men of death" in 1918. However, several key
   developments in the 1900's improved the outcome for those with
   pneumonia. With the advent of penicillin and other antibiotics, modern
   surgical techniques, and intensive care in the twentieth century,
   mortality from pneumonia dropped precipitously in the developed world.
   Vaccination of infants against Haemophilus influenzae type b began in
   1988 and led to a dramatic decline in cases shortly thereafter.
   Vaccination against Streptococcus pneumoniae in adults began in 1977
   and in children began in 2000, resulting in a similar decline.

   Retrieved from " http://en.wikipedia.org/wiki/Pneumonia"
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