What Are the Four Stages of Pneumonia?

Reviewed on 9/15/2020

What Is Pneumonia?

Lobar pneumonia is a specific type of pneumonia that has four stages.
Lobar pneumonia is a specific type of pneumonia that has four stages.

Pneumonia is an infection of the lungs that causes cough, fever, and trouble breathing. It can cause serious illness in young children, people over age 65, and people with other health problems. Pneumonia may affect one or both lungs.

What Are Symptoms of Pneumonia?

Common symptoms of pneumonia include:

  • Cough: cough may produce phlegm or mucus that may be greenish, yellow, or bloody
  • Fever 
  • Difficulty breathing
  • Shortness of breath
  • Rapid, shallow breathing
  • Sharp pain on inhalation or when coughing
  • Fast heartbeat
  • Sweating
  • Chills and shaking 
  • Loss of appetite
  • Lack of energy
  • Fatigue
  • Nausea and vomiting, especially in small children
  • Confusion, especially in older people

What Causes Pneumonia?

Common causes of pneumonia include bacteria, viruses, and fungi. 

Typical bacteria that cause pneumonia include:

  • S. pneumoniae (most common bacterial cause)
  • Haemophilus influenzae
  • Moraxella catarrhalis
  • Staphylococcus aureus
  • Group A streptococci
  • Aerobic gram-negative bacteria (e.g., Enterobacteriaceae such as Klebsiella spp or Escherichia coli)
  • Microaerophilic bacteria and anaerobes (associated with aspiration)

Atypical bacteria that cause pneumonia include:

  • Legionella spp
  • Mycoplasma pneumoniae
  • Chlamydia pneumoniae
  • Chlamydia psittaci
  • Coxiella burnetii

Respiratory viruses that cause pneumonia include:

  • Influenza (“flu”) A and B viruses
  • Rhinoviruses
  • Parainfluenza viruses
  • Adenoviruses
  • Respiratory syncytial virus
  • Coronaviruses (e.g., Middle East respiratory syndrome coronavirus, COVID-19)
  • Human metapneumovirus
  • Human bocaviruses

How Is Pneumonia Diagnosed?

Pneumonia is diagnosed with a history and physical exam, in which a doctor will check the lungs with a stethoscope to listen for crackling, bubbling, and rumbling sounds on inhalation.

Tests to confirm pneumonia include: 

  • Blood tests 
  • Sputum test on a sample of mucus (sputum) taken after a deep cough
  • Urinary antigen testing for S. pneumoniae
  • Chest X-ray 
  • Pulse oximetry to measure the blood oxygen levels
  • Computerized tomography (CT) scan of the chest 
  • Arterial blood gas test, to measure the amount of oxygen in a blood sample from an artery
  • Pleural fluid culture, in which a small amount of fluid is removed from tissues surrounding the lung
  • Bronchoscopy, in which a tube with a light on the end is used to look into the airways

What Is the Treatment for Pneumonia?

Treatment for pneumonia depends on the type of pneumonia, how sick the patient is, the patient’s age, and if they have other health conditions. 

Medications used to treat pneumonia include:

  • Antibiotics, if the cause is bacterial
  • Antivirals, if the cause is viral

In many cases, managing symptoms and resting are sufficient. Home care may include:

  • Getting a lot of rest
  • Drinking plenty of fluids 
  • Warm beverages can help open airways
  • Fever reducers 
  • Taking steamy baths or showers or using a humidifier to help open airways 
  • Don’t smoke and avoid secondhand smoke or any other lung irritants
  • Talk to your doctor before you take cough medicines because coughing helps the body work to get rid of infection

For severe cases, patients may need to be hospitalized, and treatment may include:

  • Intravenous (IV) fluids
  • Intravenous antibiotics
  • Oxygen therapy
  • Other breathing treatments


What is pneumonia? See Answer

What Are Complications of Pneumonia?

Complications of pneumonia are more likely to occur in very young children, older adults, people with compromised immune systems, and people who have other chronic medical problems such as diabetes or cirrhosis of the liver.

Complications of pneumonia may include:

What Is the Staging for Pneumonia?

A type of pneumonia, called lobar pneumonia, has 4 stages of development and resolution which include:

  1. In the first stage, which occurs within 24 hours of infection, the lung has increased blood flow and swelling to the airways, but only a few bacteria or white blood cells to fight infection are present. 
  2. The second stage (day 2-3), is characterized by white and red blood cells and damaged cellular debris clogging the airways and air-sacs (alveoli) and an increase in bacteria. 
  3. In the third stage (day 4-6), the lung has accumulation of more damaged red blood cells and an increase in fibrin as the debris thins out and becomes more fluid-like (exudative).
  4. The fourth and final stage, called resolution (day 7-10), is characterized by resorption of inflammatory fluids and cellular debris and restoration of the normal airways and air-sacs. Residual inflammation may lead to chronic narrowing of airways and scar tissue (pleural adhesions).

How Do You Prevent Pneumonia?

Patients can reduce their risk of getting pneumonia in some cases. 

  • Get vaccinated
  • Wash hands frequently with soap and warm water for at least 20 seconds
    • Get an annual flu shot. Flu is a common cause of pneumonia. 
    • Children under age 5, adults 65 and older, and patients at increased risk of pneumococcal disease due to other health conditions should get pneumococcal pneumonia vaccine, a common form of bacterial pneumonia  
    • In children: Hib vaccine, which prevents pneumonia in children from Haemophilus influenza type b
    • Other vaccines that can prevent infections by bacteria and viruses that may lead to pneumonia, including pertussis (whooping cough), chicken pox, and measles. Wash Your Hands
  • Wash hands frequently with soap and warm water for at least 20 seconds
  • Don't smoke
  • Eat a healthy diet, exercise regularly, and get adequate sleep to stay healthy
  • Synagis (palivizumab) may be given to some children younger than 24 months to prevent pneumonia caused by respiratory syncytial virus (RSV)

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Reviewed on 9/15/2020
Medscape Medical Reference