Pneumonia is a lung infection that’s caused by bacteria, viruses, or fungi. It ranges from mild to severe. Some cases of pneumonia occur as a complication of another infection, like influenza or COVID-19. It can affect the entirety of your lungs or only certain portions.

Your lungs are divided into five lobes — an upper, middle lobe, and lower lobe on the right as well as an upper and lower lobe on the left.

While there are many types of pneumonia based on the organism that caused the infection, pneumonia is generally divided into two major groups based on how much of your lungs is affected.

Depending on which lobes or areas of your respiratory system are affected, you may be diagnosed with:

  • Bronchopneumonia. Bronchopneumonia is a type of pneumonia that mostly affects the bronchi and bronchioles. These are the system of tubes that bring air into your lungs. This type of pneumonia often spreads to other parts of the lungs if not treated effectively.
  • Lobar pneumonia. This refers to any type of pneumonia that causes congestion or inflammation — a condition known as consolidation — which affects an entire lobe of your lung.

When bronchopneumonia moves out of its initial stage, it’s usually progressed to lobar pneumonia. Lobar pneumonia has four distinct phases of infection.

Pneumonia remains a leading cause of death worldwide. Lobar pneumonia is typically the more fatal form of this infection because it tends to encompass the entirety of the lobe.

While lobar pneumonia is usually described as moving through phases, new research suggests that severe illness or even death can occur in any of these stages, and you may not move through these stages in an orderly fashion. It’s also possible for you to be in more than one stage of this progression at a time.

Typically, these stages are used to help guide treatment and grade the severity of a lobar pneumonia infection. Below is an explanation of each stage.

1. Congestion

This is typically the first stage of infection that occurs after a pneumonia infection has dominated one of the lobes in your lung. The congestion stage typically lasts around 24 hours, and your lungs become inflamed, red, and weighed down by infection. Microscopic examination of your lung tissue in this phase would show engorged blood vessels and swelling in the tiny air sacs of your lungs (alveoli) where carbon dioxide and oxygen are exchanged.

2. Red hepatization

This is traditionally recognized at the second stage of lobar pneumonia, and it usually lasts for a few days. During this time, immune cells accumulate in large numbers in the spaces around your alveoli as they try to fight off the infection. Swelling around the alveoli is replaced with strands of fibrous tissue, and your lung tissue becomes dry and firm. In this stage, your alveoli are not able to move oxygen and other gases into your bloodstream as well. The red blood cells that carry oxygen and other nutrients can burst and leak, giving your lung tissue a pink or red appearance under a microscope.

3. Gray hepatization

This stage usually appears 2 to 3 days after the red hepatization stage and can last for up to 8 days. Fibrous tissue and secretions increase as red blood cells are destroyed. Hemosiderin, a protein that stores iron in your tissues, may accumulate. These changes in your cells and tissues can create staining or discoloration of your lung tissue, giving a gray or darkened appearance on microscopic examination.

4. Resolution

If you have reached the resolution phase, enzymes and other immune cells have been able to mount a defense against the infection and dissolve fibrous growths that restricted gas exchange. Immune cells called macrophages clear dead tissue debris, and your alveoli function begins to recover.

The symptoms you experience with pneumonia can depend on whether it was caused by bacteria, a virus, or fungus, and your overall health. Below are examples of some symptoms you may notice as lobar pneumonia progresses.

Symptoms during the congestion phase

In the early phase of pneumonia, you may experience things like:

  • congestion
  • fever
  • fatigue
  • wet cough with sputum (phlegm)
  • chest pain

Symptoms during the red hepatization phase

As you move into more advanced stages of pneumonia, you may be increasingly weak or tired as your body tries to fight the infection. You may start to see sputum production or coughing decrease as swelling in the alveoli increases. When this happens, you may become short of breath or have difficulty breathing.

Symptoms during the gray hepatization phase

This is the more severe phase of lobar pneumonia, and while you may not notice as much coughing or sputum production, shortness of breath is common. Your alveoli are surrounded by swelling and fibrous strands that keep them from moving gases like oxygen in and out of your bloodstream.

Medical emergency

You might have symptoms of hypoxia as your gas exchange is impaired. This is a life threatening emergency. Call emergency services or go to the nearest emergency room if you experience:

  • a blueish tinge to your lips or nail beds
  • severe shortness of breath
  • dizziness
  • confusion
  • a rapid heartbeat
  • shallow breathing

In this stage, supplemental oxygen or even mechanical ventilation may be required to prevent additional complications from hypoxia.

Symptoms during the resolution phase

In the resolution phase, your infection is beginning to clear. You may have more energy, and your shortness of breath may be improving. However, you could also notice an increase or return in coughing and sputum production as your body works to clear dead tissues and other debris from your lungs.

It can be difficult to tell the difference between any type of cold or respiratory infection and pneumonia in the early stages. Many respiratory infections can cause a cough that’s either wet or dry and begins to clear in 2 to 3 weeks. If your cough is lasting longer, or becoming more severe during that time even with medication, you may want to see a doctor.

Medical emergency

If you begin to experience signs of more severe infection like a fever above 102°F or confusion, or if you start to have trouble breathing, you should see a doctor right away.

If you can’t quickly make an appointment quickly with a doctor or you have severe breathing trouble, seek care immediately at an emergency department.

How you are treated for pneumonia will depend on the infection that triggered it and how sick you become. Antibiotics are typically used to treat pneumonia, but viral and fungal pneumonia may require alternative treatments.

Early pneumonia

In early phases of pneumonia like the congestion phase, or in people who don’t have other significant health conditions that could complicate the pneumonia, broad-spectrum antibiotics designed to treat a variety of infections are usually offered without testing to confirm your specific strain of pneumonia. This may include antibiotics like:

These antibiotics target the most common causes of pneumonia. You may also find relief with treatments like:

  • fluids to thin your secretions and mucus
  • rest
  • medications to control your fever
  • using a humidifier


Speak with a doctor before taking over-the-counter cough and cold medications for pneumonia. Some medications can cause drying, which may make your symptoms worse.

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Severe or complicated pneumonia

As you move into the red or gray hepatization phases of pneumonia, you may need to be treated with intravenous antibiotics or fluids. You may also require supplemental oxygen.

Medications used in more severe cases of pneumonia requiring inpatient care usually include formulas that combine more than one type of antibiotic, such as:

  • fluoroquinolones
  • beta-lactams
  • cephalosporin
  • macrolides

Viral pneumonia caused by influenza may also require the use of oseltamivir, an antiviral medication, which is predominantly used to shorten the course of viral pneumonia.

In severe cases, you may also need direct drainage of fluids from your lungs with a chest tube.

A chest tube could be used if a person develops a parapneumonic effusion, which is not in the lungs but around the lungs in the thoracic cavity, which is also known as the pleural space.

You will be observed closely for any complications if you have other health conditions like:

  • kidney disease
  • liver disease
  • cancer
  • other lung conditions

People with other conditions are more likely to have pneumonia that progresses to sepsis or multi-organ failure and even death.

Pneumonia can be serious and even fatal.

Lobar pneumonia is the most serious type. It develops when one or more of the five lobes in your lung becomes completely congested by the infection. When this happens, your lung tissue is unable to move oxygen and other gases in and out of your blood, and serious complications may develop.

If you think you may have pneumonia, or if you experience symptoms like shortness of breath or confusion after a period of illness, see a doctor. Pneumonia can progress through several stages, but medical care is important in all of them.