Pneumonia
The alveoli are tiny air sacs within the lungs that normally allow oxygen to enter the bloodstream. Pneumonia occurs when these small spaces fill with fluid or pus, creating inflammation known as pneumonitis. This blockage prevents proper gas exchange and leads to difficulty breathing. The condition can range from mild cases requiring rest to severe illness demanding intensive care. Medical professionals classify this state based on where the infection was acquired, such as community settings or hospital environments. The term pneumonia specifically refers to lung inflammation caused by infection, though it sometimes includes non-infectious causes like chemical burns.
Bacteria remain the most common cause of community-acquired pneumonia, with Streptococcus pneumoniae isolated in nearly 50% of cases. Other frequently identified bacteria include Haemophilus influenzae at 20%, Chlamydia pneumoniae at 13%, and Mycoplasma pneumoniae at 3%. Viruses account for about one third of adult cases and 15% of pediatric infections. Common viral agents include rhinoviruses, coronaviruses, influenza virus, respiratory syncytial virus, adenovirus, and parainfluenza. Fungal infections occur more often in individuals with weakened immune systems due to AIDS or immunosuppressive drugs. Parasites such as Toxoplasma gondii and Strongyloides stercoralis can also affect the lungs through direct contact or insect vectors. Mixed infections involving both viruses and bacteria happen in roughly 45% of childhood cases and 15% of adult cases.
Symptoms typically include a productive cough, fever accompanied by shaking chills, shortness of breath, and sharp chest pain during deep breaths. In elderly people, confusion may be the most prominent sign instead of classic respiratory symptoms. Children under five years old present with fever, cough, and fast breathing rates exceeding 60 breaths per minute if they are younger than two months. A rapid respiratory rate is defined as greater than 50 breaths per minute for children aged two months to one year. Chest X-rays remain frequently used in diagnosis, though lung ultrasonography has gained prominence in expert hands. Physical examination may reveal low blood pressure, high heart rate, or decreased oxygen saturation. Crackles heard over the affected area during inspiration help distinguish pneumonia from other conditions like pleural effusion.
Vaccines prevent certain bacterial and viral pneumonias in both children and adults. The Centers for Disease Control and Prevention recommends yearly influenza vaccination for every person six months and older. Immunizing healthcare workers decreases the risk of viral pneumonia among their patients. Strong evidence supports vaccinating children under age two against Streptococcus pneumoniae using the pneumococcal conjugate vaccine. A Streptococcus pneumoniae vaccine available for adults reduces the risk of invasive pneumococcal disease by 74%. In October 2024, the CDC lowered the age for adult pneumococcal vaccination from 65 to 50 years old. Smoking cessation and reducing indoor air pollution from cooking with wood or dung are also recommended preventative measures. Exclusive breastfeeding for infants less than six months reduces both the risk and severity of the disease.
Antibiotics improve outcomes in those with bacterial pneumonia when administered as soon as possible. Treatment duration has traditionally been seven to ten days, but shorter courses of three to five days may be effective for certain types. For adults requiring hospitalization, a beta-lactam such as cephazolin plus a macrolide like azithromycin is often recommended. Severe cases may require mechanical ventilation through an endotracheal tube if oxygen levels remain critically low. Mortality rates vary significantly based on patient status, reaching 30% to 50% for those requiring intensive care. Most people stabilize within three to six days after treatment begins, though full symptom resolution can take weeks. About 10% of discharged patients are readmitted due to underlying comorbidities or new onset of pneumonia.
Edwin Klebs was the first to observe bacteria in the airways of persons dying from pneumonia in 1875. Initial work identifying common bacterial causes was performed by Carl Friedländer and Albert Fraenkel in 1882 and 1884 respectively. Christian Gram's paper describing the Gram stain procedure in 1884 helped differentiate these two bacteria. Sir William Osler described pneumonia as the captain of men of death in 1918 when it overtook tuberculosis as a leading cause of death. Viral pneumonia was first described by Hobart Reimann in 1938 at Jefferson Medical College. With the advent of penicillin and other antibiotics in the 20th century, mortality dropped precipitously from approximately 30%. Vaccination against Haemophilus influenzae type B began in 1988, leading to a dramatic decline in cases shortly thereafter.
Pneumonia affects approximately 450 million people annually worldwide, resulting in about four million deaths each year. Rates are greatest in children less than five years old and adults older than 75 years. The disease occurs about five times more frequently in the developing world than in the developed world. In 2008, pneumonia occurred in approximately 156 million children, with 151 million cases occurring in the developing world. Countries with the greatest burden include India with 43 million cases, China with 21 million, and Pakistan with 10 million. The global economic cost has been estimated at 17 billion dollars annually for community-acquired pneumonia alone. In 2012, aggregate costs of treating pneumonia in the United States were 20 billion dollars, with median hospitalization costs exceeding 15,000 dollars per case.
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Common questions
What is pneumonia and how does it affect the lungs?
Pneumonia is inflammation of the alveoli in the lungs that occurs when these small air sacs fill with fluid or pus. This blockage prevents proper gas exchange and leads to difficulty breathing.
Which bacteria cause community-acquired pneumonia most frequently?
Streptococcus pneumoniae remains the most common cause of community-acquired pneumonia, isolated in nearly 50% of cases. Other frequently identified bacteria include Haemophilus influenzae at 20%, Chlamydia pneumoniae at 13%, and Mycoplasma pneumoniae at 3%.
How old must a person be to receive the adult pneumococcal vaccination according to October 2024 guidelines?
In October 2024, the Centers for Disease Control and Prevention lowered the age for adult pneumococcal vaccination from 65 to 50 years old. A Streptococcus pneumoniae vaccine available for adults reduces the risk of invasive pneumococcal disease by 74%.
When did Edwin Klebs first observe bacteria in the airways of persons dying from pneumonia?
Edwin Klebs was the first to observe bacteria in the airways of persons dying from pneumonia in 1875. Initial work identifying common bacterial causes followed with Carl Friedländer and Albert Fraenkel in 1882 and 1884 respectively.
How many people die from pneumonia annually worldwide?
Pneumonia affects approximately 450 million people annually worldwide, resulting in about four million deaths each year. Rates are greatest in children less than five years old and adults older than 75 years.