Pneumonia

Pneumonia is an inflammatory condition of the lung affecting primarily the microscopic air sacs known as alveoli. It is usually caused by infection with viruses or bacteria and less commonly other microorganisms, certain drugs and other conditions such as autoimmune diseases.

Typical signs and symptoms include a cough, chest pain, fever, and difficulty breathing.

• Bacterial pneumonia, which is the most common form, tends to be more serious than other types of pneumonia, with symptoms that require medical care. The symptoms of bacterial pneumonia can develop gradually or suddenly. Fever may rise as high as a dangerous 105 degrees F, with profuse sweating and rapidly increased breathing and pulse rate. Lips and nailbeds may have a bluish color due to lack of oxygen in the blood. A patient's mental state may be confused or delirious.
• The symptoms of viral pneumonia usually develop over a period of several days. Early symptoms are similar to influenza symptoms: fever, a dry cough, headache, muscle pain, and weakness. Within a day or two, the symptoms typically get worse, with increasing cough, shortness of breath and muscle pain. There may be a high fever and there may be blueness of the lips.
• Symptoms may vary in certain populations.
  • Newborns and infants may not show any signs of the infection. Or, they may vomit, have a fever and cough, or appear restless, sick, or tired and without energy.
  • Older adults and people who have serious illnesses or weak immune systems may have fewer and milder symptoms. They may even have a lower-than-normal temperature. Older adults who have pneumonia sometimes have sudden changes in mental awareness.
  • People with an underlying health condition or weakened immune system.
  • People receiving chemotherapy or taking medication that suppresses the immune system.
  • For individuals that already have a chronic lung disease, those symptoms may worsen.

Causes:

• Many germs can cause pneumonia. The most common are bacteria and viruses in the air we breathe. The body usually prevents these germs from infecting the lungs. But sometimes these germs can overpower the immune system, even if a person’s health is generally good.
• Fungi. This type of pneumonia is most common in people with chronic health problems or weakened immune systems, and in people who have inhaled large doses of the organisms. The fungi that cause it can be found in soil or bird droppings and vary depending upon geographic location.
• Viruses, including COVID-19. Some of the viruses that cause colds and the flu can cause pneumonia. Viruses are the most common cause of pneumonia in children younger than 5 years. Viral pneumonia is usually mild. But in some cases it can become very serious. Coronavirus 2019 (COVID-19) may cause pneumonia, which can become severe.
• Aspiration pneumonia occurs when you inhale food, drink, vomit or saliva into your lungs. Aspiration is more likely if something disturbs your normal gag reflex, such as a brain injury or swallowing problem, or excessive use of alcohol or drugs.

Diagnostic tools include

• Blood tests to confirm the infection and to try to identify the germ that is causing illness.
• Chest X-rays to look for the location and extent of inflammation
• Culture of the sputum to look for the source of the infection.
• For those who are considered a high-risk patient because of age and overall health, or are hospitalized, the doctors may want to do some additional tests, including:
  • CT scan of the chest to get a better view of the lungs and look for abscesses or other complications.
  • Arterial blood gas test, to measure the amount of oxygen in a blood sample taken from an artery, usually in your wrist. This is more accurate than the simpler pulse oximetry.
  • Pleural fluid culture, which removes a small amount of fluid from around tissues that surround the lung, to analyze and identify bacteria causing the pneumonia.
  • Bronchoscopy, a procedure used to look into the lungs' airways. If hospitalized and treatment is not working well, doctors may want to see whether something else is affecting the airways, such as a blockage. They may also take fluid samples or a biopsy of lung tissue.

Prognosis

• With treatment, most types of bacterial pneumonia will stabilize in 3–6 days.
• Pneumonia is the most common hospital-acquired infection that causes death.[27] Before the advent of antibiotics, mortality was typically 30% in those that were hospitalized.

Treatment

• Vaccines to prevent certain types of pneumonia are available.
• Treatment depends on the underlying cause. Pneumonia presumed to be bacterial is treated with antibiotics. If the pneumonia is severe, the affected person is generally hospitalized.

Epidemiology / Statistics

• Pneumonia affects approximately 450 million people globally per year (7% of the population) and results in about 4 million deaths. Although pneumonia was regarded by William Osler in the 19th century as "the captain of the men of death," the advent of antibiotic therapy and vaccines in the 20th century has seen improvements in survival. Nevertheless, in developing countries, and among the very old, the very young, and the chronically ill, pneumonia remains a leading cause of death. In the terminally ill and elderly, especially those with other conditions, pneumonia is often the immediate cause of death. In such cases, particularly when it cuts short the suffering associated with lingering illness, pneumonia has often been called "the old man's friend."
• Pneumonia accounts for 14% of all deaths of children under 5 years old, killing 740 180 children in 2019
• Rates are greatest in children less than five, and adults older than 75 years.[
• It occurs about five times more frequently in the developing world than in the developed world.
• Viral pneumonia accounts for about 200 million cases.
• In the United States, as of 2009, pneumonia is the 8th leading cause of death.

Resources & additional reading

• American Lung Association - What Are the Symptoms of Pneumonia?
• Mayo Clinic - Pneumonia
• WebMD - Pneumonia
• WHO - Pneumonia
• CDC - Pneumonia an infection of the lungs
• Wikipedia - Pneumonia

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