Pneumonia is an infection that inflames the air sacs (alveoli) in one or both lungs. The air sacs may fill with fluid or pus (purulent material), causing cough with phlegm or pus, fever, chills, and difficulty breathing. A variety of organisms, including bacteria, viruses and fungi, can cause pneumonia. Pneumonia can range in seriousness from mild to life-threatening. It is most serious for infants and young children, people older than age 65, and people with health problems or weakened immune systems.
Types of Pneumonia
Pneumonia is generally categorized into several types based on its cause:
Community-acquired pneumonia (CAP): This is the most common type of pneumonia and is contracted outside of healthcare settings. It can be caused by bacteria, viruses, fungi, or other infectious agents.
Hospital-acquired pneumonia (HAP) or nosocomial pneumonia: This type of pneumonia occurs during a hospital stay. Patients on breathing machines (ventilators) in intensive care units are particularly at risk.
Aspiration pneumonia: This type of pneumonia develops when you inhale food, drink, saliva, or vomit into your lungs. Aspiration is more likely if something disturbs your normal gag reflex, such as a brain injury or swallowing problem, or excessive alcohol use.
Ventilator-associated pneumonia (VAP): A type of HAP that occurs in people who are on breathing machines in hospitals.
Bacterial pneumonia: This is the most common cause of pneumonia. The bacteria Streptococcus pneumoniae is the most common cause of bacterial pneumonia in the United States.
Viral pneumonia: This type is caused by various viruses, including influenza (flu) viruses, respiratory syncytial virus (RSV), and rhinovirus.
Fungal pneumonia: Fungi from soil or bird droppings can cause this type of pneumonia, which is most common in people with weakened immune systems.
Causes of Pneumonia
Pneumonia is typically caused by a variety of infectious agents, including:
Bacteria: The most common cause of bacterial pneumonia is Streptococcus pneumoniae. Other bacteria that can cause pneumonia include Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumophila, and others.
Viruses: The influenza virus is the most common cause of viral pneumonia in adults. Other viruses that can cause pneumonia include respiratory syncytial virus (RSV), rhinovirus, adenovirus, and parainfluenza virus.
Fungi: Fungal pneumonia is most commonly caused by the fungi Cryptococcus, Histoplasma, Coccidioides, and Pneumocystis jirovecii.
Other causes: Pneumonia can also be caused by inhaling or aspirating foreign substances into the lungs, such as food, drink, saliva, or vomit.
Symptoms of Pneumonia
The symptoms of pneumonia can vary depending on the type of pneumonia, the age and overall health of the individual, and other factors. Common symptoms of pneumonia include:
Cough: A cough that may produce greenish, yellow, or bloody mucus.
Fever: A high fever with shaking chills.
Shortness of breath: Difficulty breathing, especially when you exert yourself.
Chest pain: Sharp or stabbing chest pain that gets worse when you breathe deeply or cough.
Fatigue: Feeling very tired or exhausted.
Nausea and vomiting: Especially in older adults and people with weak immune systems.
Confusion: Especially in older adults.
Low body temperature: In older adults and people with weak immune systems.
Stages of Pneumonia
Pneumonia typically progresses through four stages:
Consolidation: In this stage, the alveoli (air sacs) in the lungs fill with fluid and pus, causing consolidation, which is a hallmark of pneumonia. This leads to symptoms such as cough, fever, and difficulty breathing.
Red hepatization: In this stage, the affected part of the lung becomes red and firm as a result of the accumulation of red blood cells, white blood cells, and fibrin in the alveoli.
Grey hepatization: In this stage, the red blood cells and fibrin begin to break down, leading to a grayish appearance of the affected part of the lung.
Resolution: In this stage, the body’s immune system clears the infection, and the affected part of the lung returns to normal.
Diagnosis of Pneumonia
To diagnose pneumonia, your doctor will likely perform a combination of the following tests:
Physical examination: Your doctor will listen to your lungs with a stethoscope to check for abnormal breath sounds, such as crackling or wheezing.
Chest X-ray: A chest X-ray can show the extent of the infection and help determine the type of pneumonia.
Blood tests: Blood tests can help determine the cause of the infection, such as whether it is bacterial, viral, or fungal.
Sputum culture: If you are coughing up mucus, your doctor may collect a sample of your sputum and send it to a lab to identify the bacteria, virus, or fungus causing the infection.
Bronchoscopy: In some cases, your doctor may perform a bronchoscopy to look inside your lungs and collect samples of lung tissue or mucus for testing.
Treatment of Pneumonia
The treatment for pneumonia depends on the type and severity of the infection, as well as the overall health of the individual. In general, treatment may include:
Antibiotics: If the pneumonia is caused by bacteria, your doctor will prescribe antibiotics to kill the bacteria.
Antiviral medications: If the pneumonia is caused by a virus, such as influenza, your doctor may prescribe antiviral medications to help reduce the severity and duration of the infection.
Antifungal medications: If the pneumonia is caused by a fungus, such as Pneumocystis jirovecii, your doctor may prescribe antifungal medications to treat the infection.
Supportive care: In addition to medications, supportive care such as rest, fluids, and oxygen therapy may be necessary to help you recover from pneumonia.
Hospitalization: If you have severe pneumonia or underlying health conditions that increase your risk of complications, you may need to be hospitalized for treatment.
Prevention of Pneumonia
Prevention is key when it comes to pneumonia. Here are some steps you can take to reduce your risk of pneumonia:
Vaccination: Getting vaccinated can help prevent certain types of pneumonia. The pneumococcal vaccine and the influenza vaccine are especially important for people at high risk of pneumonia, such as older adults, young children, and people with weakened immune systems.
Hand hygiene: Washing your hands regularly with soap and water or using hand sanitizer can help prevent the spread of germs that can cause pneumonia.
Avoid smoking: Smoking damages your lungs and increases your risk of pneumonia. If you smoke, quitting can help reduce your risk of pneumonia and improve your overall health.
Avoiding sick people: Avoid close contact with people who have respiratory infections, such as the flu or the common cold, as these infections can increase your risk of pneumonia.
Good health habits: Eating a healthy diet, getting regular exercise, getting enough sleep, and managing stress can help keep your immune system strong and reduce your risk of pneumonia.
Conclusion
Pneumonia is a common and potentially serious infection that inflames the air sacs in one or both lungs. It can be caused by bacteria, viruses, fungi, or other infectious agents, and it can range in severity from mild to life-threatening. Common symptoms of pneumonia include cough, fever, shortness of breath, chest pain, fatigue, nausea, vomiting, and confusion. Pneumonia typically progresses through four stages: consolidation, red hepatization, grey hepatization, and resolution. Diagnosis of pneumonia may involve a physical examination, chest X-ray, blood tests, sputum culture, and bronchoscopy. Treatment for pneumonia may include antibiotics, antiviral medications, antifungal medications, supportive care, and hospitalization. Prevention strategies for pneumonia include vaccination, hand hygiene, avoiding smoking, avoiding sick people, and practicing good health habits. By taking these steps, you can reduce your risk of pneumonia and stay healthy.
