What are the 4 Stages of Pneumonia?

A 3D drawing of the human respiratory system.
  • Pneumonia is an inflammatory lung condition that develops when the air sacs fill with fluid, blood cells, and pus. This can contribute to a persistent cough, chest pain, and difficulty breathing.
  • This condition is typically caused by harmful bacteria — called bacterial pneumonia — or by other respiratory illnesses like the influenza virus or COVID-19.
  • Pneumonia normally develops in four distinct stages: early congestion, red hepatization, gray hepatization, and resolution. Each phase manifests in the body and is treated slightly differently.
  • How pneumonia is treated will vary, depending on the cause and severity of your diagnosis. It will likely involve combining prescription medications like antibiotics, with professional care like oxygen supplementation.

Pneumonia is a respiratory illness that affects around 1.5 million Americans each year. It causes inflammation and infection of the lungs, often resulting in a chronic cough and breathing difficulties.

This illness can also be fatal if left untreated and accounts for over 47,000 annual deaths in the U.S.

It is important to understand this condition and know which treatment options are available to you.

In this article, we’ll take a closer look at the different stages of pneumonia and the steps you can take to manage your symptoms and get the right treatment.

What is Pneumonia?

Pneumonia is an infection that develops in the lobes of one or both lungs when the air sacs — also called alveoli — are filled with blood cells, pus, and other liquid.

When an entire lobe of the lung becomes infected, it’s called lobar pneumonia and it requires medical attention.

Pneumonia contributes to inflammation and other symptoms like:

  • Coughing

  • Fever

  • Chills

  • Trouble breathing

  • Chest pain

Pneumonia can be a serious and potentially life-threatening condition if you don’t receive the correct medical treatment.

How Do You Contract Pneumonia?

Pneumonia can develop as the result of a viral bacterial infection caused by an organism called Streptococcus pneumoniae.

Acute bacterial infection, however, is the most common cause of this condition in adults in the U.S.

It can also be caused by acute respiratory diseases that affect the lungs and airways, like COVID-19, the flu, or the common cold.

Hospital-acquired pneumonia is also a recurring cause of infection and commonly occurs when equipment is shared between patients without being properly cleaned.

Certain fungi can also contribute to the development of fungal pneumonia, especially in people who have weakened immune systems.

Key Point: Who is Most at Risk of Developing Pneumonia?

Although anyone can get pneumonia, there are certain groups of people who are more at risk of contracting this disease.

These include:

  • Babies and children younger than two
  • Adults aged 65 and older
  • People who work in crowded environments where illnesses can spread easily
  • Individuals who work in environments where they regularly breathe in polluted air or toxic fumes
  • Smokers
  • People who regularly consume alcohol or use recreational drugs
  • Individuals with medical conditions like brain disease, HIV/AIDS, cancer, and lung diseases
  • Diabetics

What Are the Different Stages of Pneumonia?

When you contract pneumonia, the condition develops over four stages. Understanding the different stages can help you and your doctor determine how serious your condition is and help guide treatment.

Stage one: Congestion

During the first stage of pneumonia, the lungs become heavily congested due to the buildup of fluid that has accumulated in the alveoli.

You may experience early symptoms that include the following:

  • Coughing

  • A feeling of heaviness in the chest

  • Rapid breathing

  • Loss of appetite

  • Fatigue

The congestion stage usually lasts for 24 hours, during which the lungs become infected and inflamed.

Stage two: Red hepatization

In this stage, red blood and immune cells accumulate around the alveoli to help combat the infection. It can last for a few days.

During the red hepatization stage, swelling around the alveoli is replaced with fibrous tissues that dry and firm up the lung tissue.

While this is happening, the alveoli have less ability to transport oxygen and other gasses into the bloodstream.

Although the body is preparing itself to fight the disease during this phase, you might experience worsening symptoms, such as:

  • Increase in cough intensity

  • Shortness of breath

  • Muscle aches

  • Extreme fatigue

  • Headaches

  • Fever

  • Chills

  • Sweating

  • Blue lips or nails due to lower blood oxygen levels

Older people who have been infected with pneumonia may also experience bouts of confusion or delirium due to a lack of oxygen.

It’s important to monitor your symptoms — or have someone do it for you—because severe effects require professional medical care.

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Stage three: Grey hepatization

In the third phase of a pneumonia infection, fibrous tissue increases as red blood cells are destroyed. Hemosiderin proteins that store iron in the blood may also start to accumulate.

These changes in the cells and tissue are significant and can cause the lung tissue to discolor, giving it a gray appearance.

This stage usually appears around two to three days after red hepatization and can last up to eight days.

The immune cells will remain to protect the lungs and body; however, symptoms usually persist.

Stage four: Resolution

The last stage of infection — the resolution phase — is when infected patients usually start to feel better.

It typically occurs around the eighth to tenth day after infection and can last up to a few weeks.

This also means that the body’s immune system has been able to mount a defense against the infection and alveoli function is being restored.

You might find it easier to breathe as your symptoms start to resolve. Some patients develop a productive cough, which is meant to help clear fluid from the lungs.

Key Point: How Long Does it Take to Recover from Pneumonia?

A pneumonia infection usually peaks around the fourth to the sixth day of infection. Peaks can last between two to six days.

Once the infection has peaked, symptoms will typically start to resolve.

It can take a few weeks for hardened tissue and fluid to clear from the lungs, but symptoms won’t worsen during this time.

How is Pneumonia Treated?

Pneumonia should be diagnosed by a medical professional to help you determine the kind of treatment you need.

Your doctor will likely perform a physical exam and require blood tests to help make sense of your lung infection.

The treatment options that they recommend will vary according to the root cause of the disease and the severity of your diagnosis.

Let’s take a closer look at how each stage may be treated.

Early pneumonia

Early pneumonia — or the congestion phase — is usually treated with prescription medications like antibiotics. These may include:

  • Azithromycin

  • Clarithromycin

  • Levofloxacin

  • Gemifloxacin

  • Moxifloxacin

Antibiotics are used to treat a number of symptoms at the same time.

However, they’re not usually recommended for people with certain underlying conditions, as they can cause serious complications.

Symptoms of early pneumonia can also be alleviated by:

  • Resting

  • Taking over-the-counter or prescription medications to manage and control fever

  • Using a humidifier

Complicated or severe pneumonia

Complicated pneumonia is when the infection moves to the red or gray hepatization phases.

From here, treatment will likely need to be scaled up and might also require hospitalized care such as:

  • Receiving intravenous antibiotics and fluids

  • Receiving supplemental oxygen

If you’ve contracted pneumonia from a respiratory virus like influenza, you might require the use of oseltamivir — an antiviral medication used to shorten the course of viral pneumonia.

In severe cases, patients may require the use of a chest tube that drains fluids from their lungs.

Are You Concerned That You Might Have Pneumonia?

If left untreated, pneumonia can have very serious consequences. Worried about any of the symptoms we’ve covered in this article? You can speak to a doctor or nurse practitioner right from home. Head over to LifeMD to make a video appointment.

Dr. Payel Gupta

Dr. Gupta holds certifications from the American Board of Allergy and Immunology, American Board of Internal Medicine, and American Board of Pediatrics. With a deep interest in global health, she’s volunteered her clinical skills across many continents.

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This article is intended for informational purposes only and should not be considered medical advice. Consult a healthcare professional or call a doctor in the case of a medical emergency.

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