Pneumonia

People with infectious pneumonia often have a productive cough, fever accompanied by shaking chills, shortness of breath, sharp or stabbing chest pain during deep breaths, and an increased rate of breathing. The typical signs and symptoms in children under five are fever, cough, and fast or difficult breathing. Pneumonia caused by Streptococcus pneumoniae is associated with rusty colored sputum. Pneumonia caused by Klebsiella may have bloody sputum often described as "currant jelly". Bloody sputum (known as hemoptysis) may also occur with tuberculosis, Gram-negative pneumonia, lung abscesses and more commonly acute bronchitis. Pneumonia caused by Mycoplasma pneumoniae may occur in association with swelling of the lymph nodes in the neck, joint pain, or a middle ear infection. Viral pneumonia presents more commonly with wheezing than bacterial pneumonia. Pneumonia was historically divided into "typical" and "atypical" based on the belief that the presentation predicted the underlying cause. However, evidence has not supported this distinction, therefore it is no longer emphasized. ==Cause==

'', a common cause of pneumonia, imaged by an electron microscope Pneumonia is due to infections caused primarily by bacteria or viruses and less commonly by fungi and parasites. Although more than 100 strains of infectious agents have been identified, only a few are responsible for the majority of cases. Mixed infections with both viruses and bacteria may occur in roughly 45% of infections in children and 15% of infections in adults. Most patients (62%) had no detectable pathogens in their sample, and unexpectedly, respiratory viruses were detected more frequently than bacteria. Additional risks in children include not being breastfed, exposure to cigarette smoke and other air pollution, malnutrition, and poverty. The use of acid-suppressing medications – such as proton-pump inhibitors or H2 blockers – is associated with an increased risk of pneumonia. Approximately 10% of people who require mechanical ventilation develop ventilator-associated pneumonia, and people with a gastric feeding tube have an increased risk of developing aspiration pneumonia. Moreover, the misplacement of a feeding tube can lead to aspiration pneumonia. 28% of tube malposition results in pneumonia. As with Avanos Medical's feeding tube placement system, the CORTRAK* 2 EAS, which was recalled in May 2022 by the FDA due to adverse events reported, including pneumonia, caused a total of 60 injuries and 23 patient deaths, as communicated by the FDA. For people with certain variants of the FER gene, the risk of death is reduced in sepsis caused by pneumonia. However, for those with TLR6 variants, the risk of getting Legionnaires' disease is increased. Other commonly isolated bacteria include Haemophilus influenzae in 20%, Chlamydophila pneumoniae in 13%, and Mycoplasma pneumoniae in 3% of cases; After organ transplantation or in otherwise immunocompromised persons, there are high rates of cytomegalovirus pneumonia. Fungi Fungal pneumonia is uncommon, but occurs more commonly in individuals with weakened immune systems due to AIDS, immunosuppressive drugs, or other medical problems. It is most often caused by Histoplasma capsulatum, Blastomyces, Cryptococcus neoformans, Pneumocystis jiroveci (pneumocystis pneumonia, or PCP), 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, including Toxoplasma gondii, Strongyloides stercoralis, Ascaris lumbricoides, and Plasmodium malariae. These organisms typically enter the body through direct contact with the skin, ingestion, or via an insect vector. Noninfectious Idiopathic interstitial pneumonia or noninfectious pneumonia is a class of diffuse lung diseases. They include diffuse alveolar damage, organizing pneumonia, nonspecific interstitial pneumonia, lymphocytic interstitial pneumonia, desquamative interstitial pneumonia, respiratory bronchiolitis interstitial lung disease, and usual interstitial pneumonia. Lipoid pneumonia is another rare cause due to lipids entering the lung. ==Mechanisms==

with fluid, hindering oxygenation. The alveolus on the left is normal, whereas the one on the right is full of fluid from pneumonia. Pneumonia frequently starts as an upper respiratory tract infection that moves into the lower respiratory tract. It is a type of pneumonitis (lung inflammation). The normal flora of the upper airway give protection by competing with pathogens for nutrients. In the lower airways, reflexes of the glottis, actions of complement proteins and immunoglobulins are important for protection. Microaspiration of contaminated secretions can infect the lower airways and cause pneumonia. The progress of pneumonia is determined by the virulence of the organism; the amount of organism required to start an infection; and the body's immune response against the infection. The neutrophils also release cytokines, causing a general activation of the immune system. This leads to the fever, chills, and fatigue common in bacterial pneumonia. Viral Viruses may reach the lung by a number of different routes. Respiratory syncytial virus is typically contracted when people touch contaminated objects and then touch their eyes or nose. Other viral infections occur when contaminated airborne droplets are inhaled through the nose or mouth. The invasion of the lungs may lead to varying degrees of cell death. ==Diagnosis==

Pneumonia is typically diagnosed based on a combination of physical signs and often a chest X-ray. In recent years, however, the role of lung ultrasonography has gained prominence, with substantial evidence demonstrating that, in expert hands, it surpasses radiography in accuracy. In adults with normal vital signs and a normal lung examination, the diagnosis is unlikely. However, the underlying cause can be difficult to confirm, as there is no definitive test able to distinguish between bacterial and non-bacterial cause. Diagnosis in children The World Health Organization has defined pneumonia in children clinically based on either a cough or difficulty breathing and a rapid respiratory rate, chest indrawing, or a decreased level of consciousness. In children, low oxygen levels and lower chest indrawing are more sensitive than hearing chest crackles with a stethoscope or increased respiratory rate. Grunting and nasal flaring may be other useful signs in children less than five years old. Lack of wheezing is an indicator of Mycoplasma pneumoniae in children with pneumonia, but as an indicator it is not accurate enough to decide whether or not macrolide treatment should be used. The presence of chest pain in children with pneumonia doubles the probability of Mycoplasma pneumoniae. C-reactive protein (CRP) may help support the diagnosis. For those with CRP less than 20 mg/L without convincing evidence of pneumonia, antibiotics are not recommended. Antibiotics are encouraged if the procalcitonin level reaches 0.25 μg/L, strongly encouraged if it reaches 0.5 μg/L, and strongly discouraged if the level is below 0.10 μg/L. Thus, treatment is frequently based on the presence of influenza in the community or a rapid influenza test. Physical exam Physical examination may sometimes reveal low blood pressure, high heart rate, or low oxygen saturation. If a person is sufficiently sick to require hospitalization, a chest radiograph is recommended. Bacterial, community-acquired pneumonia classically show lung consolidation of one lung segmental lobe, which is known as lobar pneumonia. Ultrasound is radiation free and can be done at bedside. However, ultrasound requires specific skills to operate the machine and interpret the findings. File:UOTW 34 - Ultrasound of the Week 1.webm|Pneumonia seen by ultrasound File:UOTW 34 - Ultrasound of the Week 2.webm|Pneumonia seen by ultrasound Although positive blood culture and pleural fluid culture definitively establish the diagnosis of the type of micro-organism involved, a positive sputum culture has to be interpreted with care for the possibility of colonisation of respiratory tract. Pneumonia is most commonly classified by where or how it was acquired: community-acquired, aspiration, healthcare-associated, hospital-acquired, and ventilator-associated pneumonia. It may also be classified by the area of the lung affected: lobar, bronchial pneumonia and acute interstitial pneumonia; Pneumonia in children may additionally be classified based on signs and symptoms as non-severe, severe, or very severe. The setting in which pneumonia develops is important to treatment, Healthcare Health care–associated pneumonia (HCAP) is an infection associated with recent exposure to the health care system, ==Prevention==

Prevention includes vaccination, environmental measures, and appropriate treatment of other health problems. The Centers for Disease Control and Prevention (CDC) recommends yearly influenza vaccination for every person 6 months and older. Immunizing health care workers decreases the risk of viral pneumonia among their patients. Vaccinations against Haemophilus influenzae and Streptococcus pneumoniae have good evidence to support their use. Vaccinating children against Streptococcus pneumoniae has led to a decreased rate of these infections in adults, because many adults acquire infections from children. A Streptococcus pneumoniae vaccine is available for adults, and has been found to decrease the risk of invasive pneumococcal disease by 74%, but there is insufficient evidence to suggest using the pneumococcal vaccine to prevent pneumonia or death in the general adult population. The CDC recommends that young children and adults aged 50 or older receive the pneumococcal vaccine, as well as older children or younger adults who have an increased risk of getting pneumococcal disease. The pneumococcal vaccine has been shown to reduce the risk of community acquired pneumonia in people with chronic obstructive pulmonary disease, but does not reduce mortality or the risk of hospitalization for people with this condition. People with COPD are recommended by a number of guidelines to have a pneumococcal vaccination. Zanamivir or oseltamivir decrease the chance that people who are exposed to the virus will develop symptoms; however, it is recommended that potential side effects are taken into account. Other Smoking cessation In children less than 6 months of age, exclusive breast feeding reduces both the risk and severity of disease. and is also useful for prevention in those that are immunocompromised but do not have HIV. Testing pregnant women for Group B Streptococcus and Chlamydia trachomatis, and administering antibiotic treatment, if needed, reduces rates of pneumonia in infants; preventive measures for HIV transmission from mother to child may also be efficient. Suctioning the mouth and throat of infants with meconium-stained amniotic fluid has not been found to reduce the rate of aspiration pneumonia and may cause potential harm, thus this practice is not recommended in the majority of situations. even though there is no good evidence that one approach to mouth care is better than others in preventing nursing home acquired pneumonia. Zinc supplementation in children 2 months to five years old appears to reduce rates of pneumonia. For people with low levels of vitamin C in their diet or blood, taking vitamin C supplements may be suggested to decrease the risk of pneumonia, although there is no strong evidence of benefit. For adults and children in the hospital who require a respirator, there is no strong evidence indicating a difference between heat and moisture exchangers and heated humidifiers for preventing pneumonia. There is tentative evidence that lying flat on the back compared to semi-raised increases pneumonia risks in people who are intubated. ==Management==

Antibiotics by mouth, rest, simple analgesics, and fluids usually suffice for complete resolution. However, those with other medical conditions, the elderly, or those with significant trouble breathing may require more advanced care. If the symptoms worsen, the pneumonia does not improve with home treatment, or complications occur, hospitalization may be required. The utility of chest physiotherapy in pneumonia has not yet been determined. Over-the-counter cough medicine has not been found to be effective, nor has the use of zinc supplementation in children. There is insufficient evidence for mucolytics. Vitamin D, as of 2023, is of unclear benefit in children. Vitamin C administration in pneumonia needs further research, despite found lower mortality and reduced severity for most ill patient, although it can be given to patient of low plasma vitamin C because it is not expensive and low risk. The main impact is on the respiratory and the circulatory system. Respiratory failure not responding to normal oxygen therapy may require heated humidified high-flow therapy delivered through nasal cannulae, or in severe cases mechanical ventilation through an endotracheal tube. Bacterial Antibiotics improve outcomes in those with bacterial pneumonia. Antibiotic choice depends initially on the characteristics of the person affected, such as age, underlying health, and the location the infection was acquired. Antibiotic use is also associated with side effects such as nausea, diarrhea, dizziness, taste distortion, or headaches. The use of fluoroquinolones in uncomplicated cases is discouraged due to concerns about side-effects and generating resistance in light of there being no greater benefit. For those who require hospitalization and caught their pneumonia in the community the use of a β-lactam such as cephazolin plus a macrolide such as azithromycin is recommended. The duration of treatment has traditionally been seven to ten days, but increasing evidence suggests that shorter courses (3–5 days) may be effective for certain types of pneumonia and may reduce the risk of antibiotic resistance. Research in children showed that a shorter, 3-day course of amoxicillin was as effective as a longer, 7-day course for treating pneumonia in this population. For pneumonia that is associated with a ventilator caused by non-fermenting Gram-negative bacilli (NF-GNB), a shorter course of antibiotics increases the risk that the pneumonia will return. A 2017 review therefore recommended them in adults with severe community acquired pneumonia. Viral Neuraminidase inhibitors may be used to treat viral pneumonia caused by influenza viruses (influenza A and influenza B). The choice of antibiotic will depend on several factors, including the suspected causative organism and whether pneumonia was acquired in the community or developed in a hospital setting. Common options include clindamycin, a combination of a beta-lactam antibiotic and metronidazole, or an aminoglycoside. Corticosteroids are sometimes used in aspiration pneumonia, but there is limited evidence to support their effectiveness. to not mentioning any follow-up. ==Prognosis==

With treatment, most types of bacterial pneumonia will stabilize in 3–6 days. It often takes a few weeks before most symptoms resolve. Before the advent of antibiotics, mortality was typically 30% in those that were hospitalized. Clinical prediction rules Clinical prediction rules have been developed to more objectively predict outcomes of pneumonia. • Pneumonia severity index (or PSI Score) Occasionally, microorganisms will infect this fluid, causing an empyema. ==Epidemiology==

Pneumonia is a common illness affecting approximately 450 million people a year and occurring in all parts of the world. Children In 2008, pneumonia occurred in approximately 156 million children (151 million in the developing world and 5 million in the developed world). Countries with the greatest burden of disease include India (43 million), China (21 million) and Pakistan (10 million). It is the leading cause of death among children in low income countries. Approximately half of these deaths can be prevented, as they are caused by the bacteria for which an effective vaccine is available. The IDSA has recommended that children and infants with symptoms of CAP should be hospitalized so they have access to pediatric nursing care. In 2011, pneumonia was the most common reason for admission to the hospital after an emergency department visit in the U.S. for infants and children. ==History==

poster, 1936/1937 Pneumonia has been a common disease throughout human history. The word is from Greek πνεύμων (pneúmōn) meaning "lung". The symptoms were described by Hippocrates (–370 BC): However, Hippocrates referred to pneumonia as a disease "named by the ancients". He also reported the results of surgical drainage of empyemas. Maimonides (1135–1204 AD) observed: "The basic symptoms that occur in pneumonia and that 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. Edwin Klebs was the first to observe bacteria in the airways of persons having died of pneumonia in 1875. Initial work identifying the two common bacterial causes, Streptococcus pneumoniae and Klebsiella pneumoniae, was performed by Carl Friedländer and Albert Fraenkel in 1882 and 1884, respectively. Friedländer's initial work introduced the Gram stain, a fundamental laboratory test still used today to identify and categorize bacteria. Christian Gram's paper describing the procedure in 1884 helped to differentiate the two bacteria, and showed that pneumonia could be caused by more than one microorganism. In 1887, Jaccond demonstrated pneumonia may be caused by opportunistic bacteria always present in the lung. Sir William Osler, known as "the father of modern medicine", appreciated the death and disability caused by pneumonia, describing it as the "captain of the men of death" in 1918, as it had overtaken tuberculosis as one of the leading causes of death at the time. This phrase was originally coined by John Bunyan in reference to "consumption" (tuberculosis). Osler also described pneumonia as "the old man's friend" as death was often quick and painless when there were much slower and more painful ways to die. Several developments in the 1900s improved the outcome for those with pneumonia. With the advent of penicillin and other antibiotics, modern surgical techniques, and intensive care in the 20th century, mortality from pneumonia, which had approached 30%, 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 in 2000, resulting in a similar decline. ==Society and culture==

Awareness Due to the relatively low awareness of the disease, 12 November was declared in 2009 as the annual World Pneumonia Day, a day for concerned citizens and policy makers to take action against the disease. Costs The global economic cost of community-acquired pneumonia has been estimated at $17 billion annually. the median cost of a single pneumonia-related hospitalization is over $15,000. According to data released by the Centers for Medicare and Medicaid Services, average 2012 hospital charges for inpatient treatment of uncomplicated pneumonia in the U.S. were $24,549 and ranged as high as $124,000. The average cost of an emergency room consult for pneumonia was $943 and the average cost for medication was $66. Aggregate annual costs of treating pneumonia in Europe have been estimated at €10 billion. == References ==