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| {{Pneumonia}} | | __NOTOC__ |
| '''Editor(s)-in-Chief:''' [[C. Michael Gibson, M.S., M.D.]] [mailto:mgibson@perfuse.org] Phone:617-632-7753; [[Philip Marcus, M.D., M.P.H.]][mailto:pmarcus192@aol.com]
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| | |[[File:Siren.gif|30px|link=Community acquired pneumonia resident survival guide]]||<br>||<br> |
| | |[[Community acquired pneumonia resident survival guide|'''Resident'''<br>'''Survival'''<br>'''Guide''']] |
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| | {{Community-acquired pneumonia|classification=Classification}} |
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| ==Overview==
| | '''For the main page on pneumonia, click [[pneumonia|here]].''' |
| '''Community-acquired pneumonia''' ('''CAP'''), also known as walking pneumonia, is a [[disease]] in which individuals who have not recently been [[hospital]]ized develop an [[infection]] of the [[lung]]s. CAP is a common illness and can affect people of all ages. It often causes problems like [[breath]]ing, [[fever]], chest [[Pain and nociception|pains]], and a [[cough]]. CAP occurs when ([[alveoli]]) become filled with fluid and cannot work effectively. It occurs throughout the world and is a leading cause of illness and death. Causes of CAP include [[bacteria]], [[viruses]], [[fungi]], and [[parasites]]. CAP can be [[diagnosis|diagnosed]] by [[symptom]]s and [[physical examination]] alone, though [[x-ray]]s, examination of the [[sputum]], and other tests are often used. CAP is primarily treated with [[antibiotic]] [[medication]]. Some forms of CAP can be [[Preventive medicine|prevented]] by [[vaccination]].{{ref|Sharma}} | |
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| ==Symptoms==
| | '''For hospital-acquired pneumonia, click [[hospital-acquired pneumonia|here]].''' |
| Symptoms of CAP commonly include:
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| *[[dyspnea|problems breathing]]
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| *coughing that produces greenish or yellow [[sputum]]
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| *a high [[fever]] that may be accompanied with sweating, chills, and [[rigor (medicine)|uncontrollable shaking]]
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| *sharp or stabbing [[chest pain]]
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| *rapid, shallow breathing that is often painful
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| Less common symptoms include:
| | '''For patient information on pneumonia, click [[Pneumonia (patient information)|here]].''' |
| *the coughing up of blood ([[hemoptysis]])
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| *[[headache]]s (including migraine headaches)
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| *[[anorexia (symptom)|loss of appetite]]
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| *excessive fatigue
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| *blueness of the skin ([[cyanosis]])
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| *[[nausea]]
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| *[[vomiting]]
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| *[[diarrhea]]
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| *joint pain ([[arthralgia]])
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| *muscle aches ([[myalgia]])
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| The manifestations of pneumonia, like those for many conditions, might not be typical in older people. They might instead experience:
| | {{CMG}}; {{AE}} {{AL}}; {{NH}} |
| *new or worsening confusion
| | '''Assistant Editor-In-Chief:''' Simran Singh |
| *[[hypothermia]]
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| *falls
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| Additional symptoms for infants could include:
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| *being overly sleepy
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| *yellowing of the skin ([[jaundice]])
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| *difficulties feeding{{ref|Metaly}}
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| ==Diagnosis== | | ==[[Community-acquired pneumonia overview|Overview]]== |
| Individuals with symptoms of CAP require further evaluation. [[Physical examination]] by a health provider may reveal fever, an increased [[respiratory rate]] ([[hyperventilation|tachypnea]]), low [[blood pressure]] ([[hypotension]]), a fast [[heart rate]] ([[tachycardia]]), and/or changes in the amount of oxygen in the [[blood]]. Feeling the way the chest expands ([[palpation]]) and tapping the chest wall ([[Percussion (medicine)|percussion]]) to identify dull areas which do not [[resonance|resonate]] can identify areas of the lung which are stiff and full of fluid (consolidated). Examination of the lungs with the aid of a [[stethoscope]] can reveal several things. A lack of normal breath sounds or the presence of crackling sounds ([[rales]]) when the lungs are listened to ([[auscultation|auscultated]]) can also indicate consolidation. Increased vibration of the chest when speaking (tactile fremitus) and increased volume of whispered speech during [[auscultation]] of the chest can also reveal consolidation.{{ref|Metlay}}
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| [[Image:Pneumonia.gif|thumb|left|200px|'''Pneumonia.''' Chest x-ray showing increased shadowing in right lung (left side of image). <small>(''Source: Center for Disease Control and Prevention''.)</small>]]
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| [[X-ray]]s of the chest, examination of the [[blood]] and [[sputum]] for infectious [[microorganisms]], and [[Medical laboratory|blood tests]] are commonly used to diagnose individuals with suspected CAP based upon symptoms and physical examination. The use of each test depends on the severity of illness, local practices, and the concern for any [[Complication (medicine)|complication]]s resulting from the infection.
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| All patients with CAP should have the amount of oxygen in their blood monitored with a machine called a [[pulse oximeter]]. This helps determine how well the lungs are able to work despite infection. In some cases, analysis of [[arterial blood gas]] may be required to accurately determine the amount of oxygen in the blood. [[Complete blood count]] (CBC), a blood test, may reveal extra [[white blood cell]]s, indicating an infection. Chest x-rays and chest [[computed tomography]] (CT) can reveal areas of [[opacity]] (seen as white) which represent consolidation. A normal chest x-ray makes CAP less likely; however, CAP is sometimes not seen on x-rays because the disease is either in its initial stages or involves a part of the lung not easily seen by x-ray. In some cases, chest CT can reveal a CAP which is not present on chest x-ray. X-rays can often be misleading, as many other diseases can mimic CAP such as [[congestive heart failure|heart problems]] or other types of lung damage.{{ref|Syrjala}}
| | ==[[Community-acquired pneumonia historical perspective|Historical Perspective]]== |
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| Several tests can be performed to identify the cause of an individual's CAP. [[Blood culture]]s can be drawn to isolate any bacteria or fungi in the blood stream. Sputum [[Gram's stain]] and culture can also reveal the causative microorganism. In more severe cases, a procedure wherein a flexible scope is passed through the mouth into the lungs ([[bronchoscopy]]) can be used collect fluid for culture. Special tests can be performed if an uncommon microorganism is suspected (such as testing the urine for [[Legionella]] [[antigen]] when [[Legionellosis|Legionnaires' disease]] is a concern).
| | ==[[Community-acquired pneumonia classification|Classification]]== |
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| == Pathophysiology == | | ==[[Community-acquired pneumonia pathophysiology|Pathophysiology]]== |
| The symptoms of CAP are the result of both the invasion of the lungs by [[microorganism]]s and the [[immune system]]'s response to the infection. The mechanisms of infection are quite different for [[virus]]es and the other microorganisms.
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| ===Viruses===
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| * Viruses must invade cells in order to reproduce.
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| * Typically, a virus will reach the lungs by traveling in droplets through the [[mouth]] and [[nose]] with [[inhalation]].
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| * There, the virus invades the cells lining the airways and the alveoli.
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| * This invasion often leads cell death either through direct killing by the virus or by self-destruction through [[apoptosis]].
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| * Further damage to the lungs occurs when the immune system responds to the infection. [[White blood cell]]s, in particular [[lymphocyte]]s, are responsible for activating a variety of chemicals ([[cytokine]]s) which cause leaking of fluid into the alveoli.
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| * The combination of cellular destruction and fluid-filled alveoli interrupts the transportation of oxygen into the bloodstream.
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| * In addition to the effects on the lungs, many viruses affect other [[Organ (anatomy)|organ]]s and can lead to illness affecting many different bodily functions.
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| * Viruses also make the body more susceptible to bacterial infection; for this reason, bacterial pneumonia often complicates viral CAP.
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| ===Bacteria and fungi=== | |
| * Bacteria and fungi also typically enter the lung with inhalation, though they can reach the lung through the bloodstream if other parts of the body are infected.
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| * Often, bacteria live in parts of the [[upper respiratory tract]] and are constantly being inhaled into the alveoli.
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| * Once inside the alveoli, [[bacteria]] and [[fungus|fungi]] travel into the spaces between the cells and also between adjacent alveoli through connecting pores.
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| * This invasion triggers the [[immune system]] to respond by sending white blood cells responsible for attacking microorganisms ([[neutrophil]]s) to the lungs. The neutrophils [[phagocytosis|engulf]] and kill the offending organisms but also release cytokines which result in a general activation of the immune system.
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| * This results in the fever, chills, and fatigue common in CAP. The neutrophils, bacteria, and fluid leaked from surrounding blood vessels fill the alveoli and result in impaired oxygen transportation.
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| * Bacteria often travel from the lung into the blood stream and can result in serious illness such as [[septic shock]], in which there is low blood pressure leading to damage in multiple parts of the body including the [[brain]], [[kidney]], and [[heart]].
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| ===Parasites=== | | ==[[Community-acquired pneumonia causes|Causes]]== |
| * In general, these parasites enter the body through the skin or by being swallowed.
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| * Once inside the body, these parasites travel to the lungs, most often through the blood. There, a similar combination of cellular destruction and immune response causes disruption of oxygen transportation.
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| == Microorganisms causing CAP == | | ==[[Community-acquired pneumonia differential diagnosis|Differentiating Community-acquired pneumonia from other Diseases]]== |
| There are over a hundred microorganisms which can cause CAP. The most common types of microorganisms are different among different groups of people. Newborn [[infant]]s, [[children]], and [[adult]]s are at risk for different spectrums of disease causing microorganisms. In addition, adults with [[chronic (medicine)|chronic]] illnesses, who live in certain parts of the world, who reside in [[nursing home]]s, who have recently been treated with [[antibiotic]]s, or who are [[alcoholism|alcoholics]] are at risk for unique infections. Even when aggressive measures are taken, a definite cause for pneumonia is only identified in half the cases.
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| ===Infants=== | | ==[[Community-acquired pneumonia epidemiology and demographics|Epidemiology and Demographics]]== |
| Newborn infants can acquire lung infections prior to being born either by breathing infected [[amniotic fluid]] or by blood-borne infection across the [[placenta]]. Infants can also inhale ([[aspirate]] fluid from the [[birth]] canal as they are being born. The most important infection in newborns is caused by [[Streptococcus agalactiae]], also known as Group B Streptococcus or GBS. GBS causes at least 50% of cases of CAP in the first week of life.{{ref|Webber}} Other bacterial causes in the newborn period include ''[[Listeria monocytogenes]]'' and [[tuberculosis]]. Viruses can also be transferred from mother to child; [[herpes simplex virus]] is the most common and life-threatening, but [[adenovirus]], [[mumps]], and [[enterovirus]] can also cause disease.
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| CAP in older infants reflects increased exposure to microorganisms. Common bacterial causes include ''[[Streptococcus pneumoniae]]'', ''[[Escherichia coli]]'', ''[[Klebsiella pneumoniae]]'', ''[[Moraxella catarrhalis]]'', and ''[[Staphylococcus aureus]]''. A unique cause of CAP in this group is ''[[Chlamydia trachomatis]]'', which is acquired during birth but which does not cause pneumonia until 2-4 weeks later. Common viruses include [[respiratory syncytial virus]] (RSV), [[metapneumovirus]], [[adenovirus]], [[parainfluenza]], [[influenza]], and [[rhinovirus]]. RSV in particular is a common source of illness and hospitalization.{{ref|Abzug}} Fungi and parasites are not typically encountered in otherwise healthy infants, though maternally-derived [[syphilis]] can be a cause of CAP in this age group.
| | ==[[Community-acquired pneumonia risk factors|Risk Factors]]== |
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| ===Children=== | | ==[[Community-acquired pneumonia screening|Screening]]== |
| For the most part, children older than one month of life are at risk for the same microorganisms as adults. However, children less than five years are much less likely to have pneumonia caused by ''[[Mycoplasma pneumoniae]]'', ''[[Chlamydophila pneumoniae]]'', or ''[[Legionella|Legionella pneumophila]]''. In contrast, older children and teenagers are more likely to acquire ''[[Mycoplasma pneumoniae]]'' and ''[[Chlamydophila pneumoniae]]'' than adults.{{ref|Wubbel}}
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| ===Adults=== | | ==[[Community-acquired pneumonia natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
| The full spectrum of microorganisms are responsible for CAP in adults. Several important groups of organisms are more common among people with certain [[risk factor]]s. Identifying people at risk for these organisms is important for appropriate treatment.
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| *''Viruses''
| | ==Diagnosis== |
| :Viruses cause 20% of CAP cases. The most common viruses are [[influenza]], [[parainfluenza]], [[respiratory syncytial virus]], [[metapneumovirus]], and [[adenovirus]]. Less common viruses causing significant illness include [[varicella|chicken pox]], [[SARS]], [[H5N1|avian flu]], and [[hantavirus]].{{ref|Roux}}
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| *''Atypical organisms''
| | [[Community-acquired pneumonia severity criteria| Severity Criteria]] | [[Community-acquired pneumonia history and symptoms| History and Symptoms]] | [[Community-acquired pneumonia physical examination | Physical Examination]] | [[Community-acquired pneumonia laboratory findings |Laboratory Findings]] | [[Community-acquired pneumonia chest x ray|Chest X Ray]] | [[Community-acquired pneumonia CT|CT]] | [[Community-acquired pneumonia ultrasound|Ultrasound]] | [[Community-acquired pneumonia other diagnostic studies|Other Diagnostic Studies]] |
| :The most common bacterial causes of pneumonia are the so-called atypical bacteria ''[[Mycoplasma pneumoniae]]'' and ''[[Chlamydophila pneumoniae]].'' ''[[Legionella|Legionella pneumophila]]'' is considered atypical but is less common. Atypical organisms are more difficult to grow, respond to different antibiotics, and were discovered more recently than the typical bacteria discovered in the early [[twentieth century]].
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| *''Streptococcus pneumoniae''
| | ==Treatment== |
| :''[[Streptococcus pneumoniae]]'' is a common bacterial cause of CAP. Prior to the development of antibiotics and vaccination, it was a leading cause of death. Traditionally highly sensitive to [[penicillin]], during the [[1970s]] resistance to multiple antibiotics began to develop. Current strains of "drug resistant Streptococcus pneumoniae" or DRSP are common, accounting for twenty percent of all Streptococcus pneumoniae infections. Adults with risk factors for DRSP including being older than 65, having exposure to children in [[day care]], having alcoholism or other severe underlying disease, or recent treatment with antibiotics should initially be treated with antibiotics effective against DRSP.{{ref|Ruhe}}
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| *''Hemophilus influenzae''
| | [[Community-acquired pneumonia medical therapy|Medical Therapy]] | [[Community-acquired pneumonia primary prevention|Primary Prevention]] | [[Community-acquired pneumonia cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Community-acquired pneumonia future or investigational therapies|Future or Investigational Therapies]] |
| :''[[Haemophilus influenzae|Hemophilus influenzae]]'' is another common bacterial cause of CAP. First discovered in [[1892]], it was initially believed to be the cause of influenza because it commonly causes CAP in people who have suffered recent lung damage from viral pneumonia.
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| *''Enteric Gram negative bacteria''
| | ==Case Studies== |
| :The enteric Gram negative bacteria such as ''[[Escherichia coli]]'' and ''[[Klebsiella pneumoniae]]'' are a group of bacteria that typically live in the human [[Colon (anatomy)|intestines]]. Adults with risk factors for infection including residence in a [[nursing home]], serious [[heart]] and [[lung]] disease, and recent antibiotic use should initially be treated with antibiotics effective against Enteric Gram negative bacteria.
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| *''Pseudomonas aeruginosa''
| | [[Community-acquired pneumonia case study one|Case #1]] |
| :''[[Pseudomonas aeruginosa]]'' is an uncommon cause of CAP but is a particularly difficult bacteria to treat. Individuals who are malnourished, have a lung disease called [[bronchiectasis]], are on [[corticosteroids]], or have recently had strong antibiotics for a week or more should initially be treated with antibiotics effective against ''Pseudomonas aeruginosa''.{{ref|Lieberman}}
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| Many less common organisms cause CAP. They are typically identified because an individual has special risk factors or after treatment for the common causes has failed. These rarer causes are covered in more detail in their specific pages: [[bacterial pneumonia]], [[viral pneumonia]], [[fungal pneumonia]], and [[parasitic pneumonia]].
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| == Treatment ==
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| CAP is treated by administering an antibiotic which is effective in killing the offending microorganism as well as managing any complications of the infection. If the causative microorganism is identified, different antibiotics are tested in the laboratory in order to identify which medication will be most effective. Often, however, no microorganism is ever identified. Also, since laboratory testing can take several days, there is some delay until an organism is identified. In both cases, a person's risk factors for different organisms must be remembered when choosing the initial antibiotics (called [[empiricism|empiric]] therapy). Additional consideration must be given to the setting in which the individual will be treated. Most people will be fully treated after taking oral pills while other people need to be hospitalized for [[intravenous]] antibiotics and, possibly, [[intensive care medicine|intensive care]]. In general, all therapies in older children and adults will include treatment for atypical bacteria. Typically this is a macrolide antibiotic such as [[azithromycin]] or [[clarithromycin]] although a [[fluoroquinolone]] such as [[levofloxacin]] can substitute.
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| === ''Newborn infants'' ===
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| Most newborn infants with CAP are hospitalized and given [[intravenous]] [[ampicillin]] and [[gentamicin]] for at least ten days. This treats the common bacteria ''[[Streptococcus agalactiae]]'', ''[[Listeria monocytogenes]]'', and ''[[Escherichia coli]]''. If [[herpes simplex virus]] is the cause, intravenous [[acyclovir]] is administered for 21 days.
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| === ''Children'' ===
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| Treatment of CAP in children depends on both the age of the child and the severity of his/her illness. Children less than five do not typically receive treatment to cover atypical bacteria. If a child does not need to be hospitalized, [[amoxicillin]] for seven days is a common treatment. However, with increasing prevalence of DRSP, other agents such as cefpodoxime will most likely become more popular in the future.{{ref|Bradley}} Hospitalized children should receive intravenous [[ampicillin]], [[ceftriaxone]], or [[cefotaxime]].
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| === ''Adults'' ===
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| In [[2001]], the American Thoracic Society, drawing on work by the British and Canadian Thoracic Societies, established guidelines for the management of adults with CAP which divided individuals with CAP into four categories based upon common organisms encountered.{{ref|Neiderman}}
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| *''Healthy outpatients without risk factors''
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| :This group, the largest, is composed of otherwise healthy patients without risk factors for DRSP, enteric Gram negative bacteria, ''Pseudomonas'', or other less common causes of CAP. The primary microoganisms in this group are viruses, atypical bacteria, penicillin sensitive ''Streptococcus pneumoniae'', and ''Hemophilus influenzae''. Recommended management is with a macrolide antibiotic such as [[azithromycin]] or [[clarithromycin]] for seven<ref name="pmid17765048">
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| Li JZ, Winston LG, Moore DH, Bent S. Efficacy of short-course antibiotic regimens for community-acquired pneumonia: a meta-analysis. Am J Med. 2007 Sep;120(9):783-90. PMID 17765048</ref> to ten days.
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| *''Outpatients with underlying illness and/or risk factors''
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| :This group does not require hospitalization; its members either have underlying health problems (such as [[emphysema]] or [[congestive heart failure]]) or is at risk for DRSP and/or enteric Gram negative bacteria. Treatment is with a [[fluoroquinolone]] active against ''Streptococcus pneumoniae'' such as [[levofloxacin]] or a [[beta-lactam antibiotic]] such as [[cefpodoxime]], [[cefuroxime]], [[amoxicillin]], or [[Co-amoxiclav|amoxicillin/clavulanate]] plus a macrolide antibiotic such as [[azithromycin]] or [[clarithromycin]] for seven to ten days.
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| *''Hospitalized individuals not at risk for Pseudomonas''
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| :This group requires hospitalization and administration of intravenous antibiotics. Treatment is with either an intravenous [[fluoroquinolone]] active against ''Streptococcus pneumoniae'' such as [[levofloxacin]] or [[beta-lactam antibiotic]] such as cefotaxime, ceftriaxone, ampicillin/sulbactam, or high-dose ampicillin plus an intravenous macrolide antibiotic such as [[azithromycin]] or [[clarithromycin]] for seven to ten days. | |
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| *''Individuals requiring intensive care at risk for Pseudomonas''
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| :Individuals being treated in an intensive care unit with risk factors for infection with ''Pseudomonas aeruginosa'' require specific antibiotics targeting this difficult to eradicate bacteria. One possible regimen is an intravenous antipseudomonal beta-lactam such as [[cefepime]], [[imipenem]], [[meropenem]], or [[piperacillin|piperacillin/tazobactam]] plus an intravenous antipseudomonal fluoroquinolone such as [[levofloxacin]]. Another recommended regimen is an intravenous antipseudomonal beta-lactam such as cefepime, imipenem, meropenem, or piperacillin/ tazobactam plus an intravenous aminoglycoside such as [[gentamicin]] or [[tobramycin]] plus either an intravenous macrolide such azithromycin or an intravenous nonpseudomonal fluoroquinolone such as [[ciprofloxacin]].
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| === The decision to hospitalize ===
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| Some people with CAP require hospitalization and more intensive care than the majority. In general, a discussion between the individual and his or her health care provider determines the need for hospitalization. [[Clinical prediction rule]]s, such as the [[pneumonia severity index]] and [[CURB-65]] have been developed to help guide the decision.{{ref|Fine}} Factors which increase the need for hospitalization include age greater than 65; underlying chronic illnesses; a [[respiratory rate]] greater than thirty breaths per minute; a systolic [[blood pressure]] less than 90 mmHg; a [[heart rate]] greater than 125 per minute; [[temperature]] less than 35 or greater than 40°C; confusion; and evidence of infection outside the lung. Laboratory results which increase the need for hospitalization include arterial oxygen tension less than 60 mm Hg, [[carbon dioxide]] of greater than 50 mmHg, or [[pH]] less than 7.35 while breathing room air; [[hematocrit]] less than 30%; [[creatinine]] greater than 1.2 mg/dl or [[blood urea nitrogen]] greater than 20 mg/ dl; white blood cell count less than 4 × 10^9/L or greater than 30 × 10^9/L; and absolute neutrophil count less than 1 x 10^9/L. X-ray findings which increase the need for hospitalization include involvement of more than one lobe of the [[lung]], presence of a cavity, and the presence of a [[pleural effusion]].
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| == Prognosis ==
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| * Individuals who are treated for CAP outside of the hospital have a mortality rate less than 1%.
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| * Fever typically responds in the first two days of therapy and other symptoms resolve in the first week.
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| * The x-ray, however, may remain abnormal for at least a month, even when CAP has been successfully treated.
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| * Among individuals who require hospitalization, the mortality rate averages 12% overall, but is as much as 40% in people who have bloodstream infections or require intensive care.{{ref|Woodhead}}
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| * When CAP does not respond as expected, there are several possible causes.
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| ** A complication of CAP may have occurred or a previously unknown health problem may be playing a role.
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| ** Additional causes include inappropriate antibiotics for the causative organism (ie DRSP), a previously unsuspected microorganism (such as [[tuberculosis]]), or a condition which mimics CAP (such as [[Wegener's granulomatosis]]).
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| ** Additional testing may be performed and may include additional radiologic imaging (such as a [[Computed tomography|computed tomography scan]]) or a procedure such as a [[bronchoscopy]] or lung [[biopsy]].
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| == Complications of CAP ==
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| Despite appropriate antibiotic therapy, severe complications can result from CAP, including:
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| === ''Sepsis'' ===
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| [[Sepsis]] can occur when microorganisms enter the blood stream and the [[immune system]] responds. Sepsis most often occurs with [[bacterial pneumonia]]; ''Streptococcus pneumoniae'' is the most common cause. Individuals with sepsis require hospitalization in an intensive care unit. They often require medications and intravenous fluids to keep their blood pressure from going too low. Sepsis can cause liver, kidney, and heart damage among other things.
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| === ''Respiratory failure'' ===
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| Because CAP affects the lungs, often individuals with CAP have difficulty breathing. If enough of the lung is involved, it may not be possible for a person to breathe enough to live without support. Non-invasive machines such as a [[bilevel positive airway pressure]] machine may be used. Otherwise, placement of a [[endotracheal tube|breathing tube]] into the mouth may be necessary and a [[Medical ventilator|ventilator]] may be used to help the person breathe.
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| === ''Pleural effusion and empyema'' ===
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| Occasionally, microorganisms from the lung will cause fluid to form in the space surrounding the lung, called the [[pleural cavity]]. If the microorganisms themselves are present, the fluid collection is often called an [[empyema]]. If pleural fluid is present in a person with CAP, the fluid should be collected with a needle ([[thoracentesis]]) and examined. Depending on the result of the examination, complete drainage of the fluid may be necessary, often with a [[chest tube]]. If the fluid is not drained, bacteria can continue to cause illness because antibiotics do not penetrate well into the pleural cavity.
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| === ''Abscess'' ===
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| Rarely, microorganisms in the lung will form a pocket of fluid and bacteria called an [[abscess]]. Abscesses can be seen on an x-ray as a cavity within the lung. Abscesses typically occur in [[aspiration pneumonia]] and most often contain a mixture of [[Anaerobic organism|anaerobic bacteria]]. Usually antibiotics are able to fully treat abscesses, but sometimes they must be drained by a [[surgery|surgeon]] or [[Interventional radiology|radiologist]].
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| == Special circumstances leading to CAP ==
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| Some people have an underlying problem which increases their risk of getting an infection. Some important situations are covered below:
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| === ''Obstruction'' ===
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| When part of the airway ([[bronchi]]) leading to the alveoli is obstructed, the lung is not able to clear fluid when it accumulates. This can lead to infection of the fluid resulting in CAP. One cause of obstruction, especially in young children, is inhalation of a foreign object such as a marble or toy. The object is lodged in the small airways and pneumonia can form in the trapped areas of lung. Another cause of obstruction is [[lung cancer]], which can grow into the airways block the flow of air.
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| === ''Lung disease'' ===
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| People with underlying lung disease are more likely to develop CAP. Diseases such as [[emphysema]] or habits such as [[Tobacco smoking|smoking]] result in more frequent and more severe bouts of CAP. In children, recurrent episodes of CAP may be the first clue to diseases such as [[cystic fibrosis]] or [[pulmonary sequestration]].
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| === ''Immune problems'' ===
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| People who have [[Immunodeficiency|immune system problems]] are more likely to get CAP. People who have [[AIDS]] are much more likely to develop CAP. Other immune problems range from severe immune deficiencies of childhood such as [[Wiskott-Aldrich syndrome]] to less severe deficiencies such as [[common variable immunodeficiency]].{{ref|Mundy}}
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| == Epidemiology and demographics==
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| ===United states of America===
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| * It is the seventh most common cause of death in the United States
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| * It causes around 500,000 hospitalizations and 65,000 deaths annually.
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| ===International===
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| * It is a common illness in all parts of the world.
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| ===Age===
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| * It is a major cause of death among all age groups.
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| * In children, the majority of deaths occur in the newborn period, with over two million worldwide deaths a year.
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| * In fact, the WHO estimates that one in three newborn infant deaths are due to pneumonia.{{ref|Garenne}}
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| * Mortality decreases with age until late adulthood; elderly individuals are particularly at risk for CAP and associated mortality.
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| ===Seasonal===
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| * Common during winter months than during other times of the year.
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| ===Gender===
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| * CAP occurs more commonly in males than females
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| ===Race===
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| * More common in blacks than Caucasians.
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| ===Mortality===
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| * Patients hospitalized with pneumonia have a mortality rate of 12-14%.
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| ===Special considerations===
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| * Individuals with underlying illnesses such as [[Alzheimer's disease]], [[cystic fibrosis]], [[emphysema]], [[tobacco smoking]], [[alcoholism]], or [[immunosuppression|immune system problems]] are at increased risk for pneumonia.{{ref|Almirall}}
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| == Prevention ==
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| In addition to treating any underlying illness which can increase a person's risk for CAP, there are several additional ways to prevent CAP. Smoking cessation is important not only for treatment of any underlying lung disease, but also because cigarette smoke interferes with many of the body's natural defenses against CAP.
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| [[Vaccination]] is important in both children and adults. Vaccinations against ''[[Haemophilus influenzae]]'' and ''[[Streptococcus pneumoniae]]'' in the first year of life have greatly reduced their role in CAP in children. A vaccine against ''[[Streptococcus pneumoniae]]'' is also available for adults and 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 who do not have a [[asplenia|spleen]]. A repeat vaccination may also be required after five or ten years.{{ref|Butler}}
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| [[Influenza]] vaccines should be given yearly to the same individuals as receive vaccination against ''[[Streptococcus pneumoniae]]''. In addition, health care workers, nursing home residents, and pregnant women should receive the vaccine.{{ref|CDC}} When an influenza outbreak is occurring, medications such as [[amantadine]], [[rimantadine]], [[zanamivir]], and [[oseltamivir]] have been shown to prevent cases of influenza.{{ref|Hayden}}
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| ==References==
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| {{Reflist}}
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| #{{note|Sharma}} [http://www.emedicine.com/med/topic1852.htm Emedicine review of bacterial pneumonia]
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| #{{note|Metaly}} Metaly JP, Schulz R, Li Y-H, Singer DE, Marrie TJ, Coley CM, Hough LJ, Obrosky DS, Kapoor WN, Fine MJ. ''Influence of age on symptoms at presentation in patients with community-acquired pneumonia.'' Arch Intern Med 1997; 157: 1453-1459 PMID 9224224
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| #{{note|Metlay}} Metlay, JP, Kapoor, WN, Fine, MJ. D''oes this patient have community-acquired pneumonia? Diagnosing pneumonia by history and physical examination.'' JAMA 1997; 278:1440. PMID 9356004
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| #{{note|Syrjala}} Syrjala H, Broas M, Suramo I, Ojala A, Lahde S. ''High resolution computed tomography for the diagnosis of community-acquired pneumonia.'' Clin Infect Dis 1998; 27: 358-363 PMID 9709887
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| #{{note|Webber}} Webber, S, Wilkinson, AR, Lindsell, D, et al. ''Neonatal pneumonia.'' Arch Dis Child 1990; 65:207.PMID 2107797
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| #{{note|Abzug}} Abzug, MJ, Beam, AC, Gyorkos, EA, Levin, MJ. ''Viral pneumonia in the first month of life.'' Pediatr Infect Dis J 1990; 9:881. PMID 2177540
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| #{{note|Wubbel}} Wubbel, L, Muniz, L, Ahmed, A, et al. ''Etiology and treatment of community-acquired pneumonia in ambulatory children. Pediatr Infect Dis J 1999; 18:98.'' PMID 10048679
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| #{{note|Roux}} de Roux, A, Marcos, MA, Garcia, E, et al. ''Viral community-acquired pneumonia in nonimmunocompromised adults.'' Chest 2004; 125:1343.PMID 15078744
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| #{{note|Ruhe}} Ruhe, JJ, Myers, L, Mushatt, D, Hasbun, R. ''High-level penicillin-nonsusceptible Streptococcus pneumoniae bacteremia: identification of a low-risk subgroup.'' Clin Infect Dis 2004; 38:508 PMID 14765343
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| #{{note|Lieberman}} Lieberman D, Schlaeffer F, Boldur I, Lieberman D, Horowitz S, Friedman MG, Leiononen M, Horovitz O, Manor E, Porath A. ''Multiple pathogens in adult patients admitted with community-acquired pneumonia: a one year prospective study of 346 consecutive patients.'' Thorax 1996; 51: 179-184 PMID 8711652
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| #{{note|Bradley}} Bradley, JS. ''Management of community-acquired pediatric pneumonia in an era of increasing antibiotic resistance and conjugate vaccines.'' Pediatr Infect Dis J 2002; 21:592. PMID 12182396
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| #{{note|Neiderman}} Niederman MS, Mandell LA, Anzueto A, Bass JB, Broughton WA, Campbell GD, Dean N, File T, Fine MJ, Gross PA, et al. ''Guidelines for the management of adults with community-acquired pneumonia: diagnosis, assessment of severity, antimicrobial therapy, and prevention.'' Am J Respir Crit Care Med 2001;163:1730–1754 PMID 11401897
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| #{{note|Mundy}} Mundy, LM, Auwaerter, PG, Oldach, D, et al. ''Community-acquired pneumonia: impact of immune status.'' Am J Respir Crit Care Med 1995; 152:1309. PMID 7551387
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| #{{note|Fine}} Fine MJ, Auble TE, Yealy DM, Hanusa BH, Weissfeld LA, Singer DE, Coley CM, Marrie TJ, Kapoor WN. ''A prediction rule to identify low-risk patients with community-acquired pneumonia.'' N Engl J Med 1997; 336: 243-250 PMID 8995086
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| #{{note|Woodhead}} Woodhead MA, MacFarlane JT, McCracken JS, Rose DH, Finch RG. ''Prospective study of the aetiology and outcome of pneumonia in the community.'' Lancet 1987; i: 671-674. PMID 2882091
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| #{{note|Garenne}} Garenne, M, Ronsmans, C, Campbell, H. ''The magnitude of mortality from acute respiratory infections in children under 5 years in developing countries.'' World Health Stat Q 1992; 45:180. PMID 1462653
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| #{{note|Almirall}} Almirall, J, Bolibar, I, Balanzo, X, Gonzalez, CA. ''Risk factors for community-acquired pneumonia in adults: A population-based case-control study.'' Eur Respir J 1999; 13:349. PMID 10065680
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| #{{note|Butler}} Butler JC, Breiman RF, Campbell JF, Lipman HB, Broome CV, Facklam RR. ''Pneumococcal polysaccharide vaccine efficacy: an evaluation of current recommendations.'' JAMA 1993; 270: 1826-1831. PMID 8411526
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| #{{note|CDC}} Centers for Disease Control and Prevention. ''Prevention and control of influenza: recommendations of the Advisory Committee on Immunization Practices (ACIP)''. MMWR 1999;48(RR-4):1-28.
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| #{{note|Hayden}} Hayden FG, Atmar RL, Schilling M, Johnson C, Poretz D, Paar D, Huson L, Ward P, Mills RG. ''Use of the selective oral neuraminidase inhibitor oseltamivir to prevent influenza.'' N Engl J Med 1999; 341: 1336-1343 PMID 10536125
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| ==References==
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| {{reflist|2}}
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| [[Category:Diseaase]]
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| [[Category:Pulmonology]] | | [[Category:Pulmonology]] |
| [[Category:Infectious disease]]
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| [[Category:Pneumonia|Pneumonia]] | | [[Category:Pneumonia|Pneumonia]] |
| [[Category:Emergency medicine]] | | [[Category:Emergency medicine]] |
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