[23] More severe signs and symptoms in children may include blue-tinged skin, unwillingness to drink, convulsions, ongoing vomiting, extremes of temperature, or a decreased level of consciousness.

Exposure to birds is associated with Chlamydia psittaci; farm animals with Coxiella burnetti; aspiration of stomach contents with anaerobic organisms; and cystic fibrosis with Pseudomonas aeruginosa and Staphylococcus aureus.

[12][45] Herpes simplex virus rarely causes pneumonia, except in groups such as newborns, persons with cancer, transplant recipients, and people with significant burns.

[47] Fungal pneumonia is uncommon, but occurs more commonly in individuals with weakened immune systems due to AIDS, immunosuppressive drugs, or other medical problems.

[49] A variety of parasites can affect the lungs, including Toxoplasma gondii, Strongyloides stercoralis, Ascaris lumbricoides, and Plasmodium malariae.

[61] 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.

[64] 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.

[41] A CT scan can give additional information in indeterminate cases[42] and provide more details in those with an unclear chest radiograph (for example occult pneumonia in chronic obstructive pulmonary disease).

[69] Microbiological evaluation is also indicated in severe pneumonia, alcoholism, asplenia, immunosuppression, HIV infection, and those being empirically treated for MRSA of pseudomonas.

[83] The setting in which pneumonia develops is important to treatment,[84][85] as it correlates to which pathogens are likely suspects,[84] which mechanisms are likely, which antibiotics are likely to work or fail,[84] and which complications can be expected based on the person's health status.

Prior stays in healthcare-related environments such as hospitals, nursing homes, or hemodialysis centers or a history of receiving domiciliary care can increase patients' risk for CAP caused by multidrug-resistant bacteria.

[23] It is believed that, if appropriate preventive measures were instituted globally, mortality among children could be reduced by 400,000; and, if proper treatment were universally available, childhood deaths could be decreased by another 600,000.

[96] 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.

[100] Testing pregnant women for Group B Streptococcus and Chlamydia trachomatis, and administering antibiotic treatment, if needed, reduces rates of pneumonia in infants;[101][102] preventive measures for HIV transmission from mother to child may also be efficient.

[103] 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,[104] thus this practice is not recommended in the majority of situations.

[118] For adults with moderate or severe acute respiratory distress syndrome (ARDS) undergoing mechanical ventilation, there is a reduction in mortality when people lie on their front for at least 12 hours a day.

[121] Antibiotic choice depends initially on the characteristics of the person affected, such as age, underlying health, and the location the infection was acquired.

[29] For people with ventilator-acquired pneumonia, the choice of antibiotic therapy will depend on the person's risk of being infected with a strain of bacteria that is multi-drug resistant.

[49] The use of granulocyte colony stimulating factor (G-CSF) along with antibiotics does not appear to reduce mortality and routine use for treating pneumonia is not supported by evidence.

[12] No specific antiviral medications are recommended for other types of community acquired viral pneumonias including SARS coronavirus, adenovirus, hantavirus, and parainfluenza virus.

[137] 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.

[140] This may include, among others: empyema, lung abscess, bronchiolitis obliterans, acute respiratory distress syndrome, sepsis, and worsening of underlying health problems.

This stiffness, combined with severe difficulties extracting oxygen due to the alveolar fluid, may require long periods of mechanical ventilation for survival.

[152] The symptoms were described by Hippocrates (c. 460–370 BC):[151] "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 color, or likewise thin, frothy, and florid, or having any other character different from the common...

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.

"[154] 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.

Friedländer's initial work introduced the Gram stain, a fundamental laboratory test still used today to identify and categorize bacteria.

Reimann, Chairman of the Department of Medicine at Jefferson Medical College, had established the practice of routinely typing the pneumococcal organism in cases where pneumonia presented.

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.

[168] 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.