The Four Stages of Pneumonia from Early Symptoms to Recovery (2024)

A bout of pneumonia happens in four stages: congestion, red hepatization, grey hepatization, and resolution. The names of each stage refer to how the infection develops over time.

The initial congestion stage is characterized by a wet cough, chest pain, and fever. Symptoms usually worsen in the hepatization stages, and you may have difficulty breathing. The infection typically resolves within one to two weeks. The exact symptoms may depend on your age, overall health, and the type of germ responsible (bacterial vs. viral).

This article discusses the progression of pneumonia from early to late stages. It also touches on how these stages can differ in people who receive treatment versus those who do not.

Congestion

The first stage of pneumonia is called "congestion" because it is characterized by congestion in the lungs.

Specifically, pneumonia causes the tiny air sacs in the lungs (alveoli), as well as tiny nearby blood vessels (capillaries), to become inflamed and congested with fluid. Most of this congestion takes place during the first 24 hours after the infection develops.

As you breathe, an exchange of oxygen and carbon dioxide takes place between the capillaries and the alveoli. Since these are the primary structures affected by pneumonia, you will start to notice more breathing-related symptoms as the infection progresses.

Fortunately, when pneumonia is detected and promptly treated during the congestion stage, it is less likely to result in complications. However, the severity of the infection depends on several factors, including your age, overall health, and whether the infection is bacterial or viral.

Symptoms

The congestion stage of pneumonia may start suddenly or gradually. Symptoms may be especially severe when pneumonia develops as a complication of another infection, such as influenza or COVID-19.

Symptoms in the congestion stage may include:

• Coughing, which may produce sputum that is clear, yellow, or green
• High fever and chills
• Chest pressure or heaviness
• Sharp chest pain that worsens with deep breaths (pleuritic chest pain)
• Shortness of breath
• Headache
• Loss of appetite
• Muscle aches (myalgia)
• Joint aches (arthralgia)
• Fatigue
• Nausea
• Vomiting
• Diarrhea

Some people may develop hypoxia (reduced oxygen level in the body) in the early stages of the infection. Symptoms include:

• A bluish tinge to the lips and fingers (cyanosis)
• Rapid respiratory rate (tachypnea)
• Rapid heart rate (tachycardia)
• Confusion
• Disorientation
• Shortness of breath (dyspnea)

In some cases, symptoms of hemoptysis (coughing up blood) may occur, even at the onset of the infection. This can be very alarming and warrants immediate medical attention in any case.

Children often experience many of the same symptoms as adults. However, in some cases the only symptom a child has is rapid breathing. Children may also develop a lack of appetite, which can lead to dehydration.

Management/Treating Symptoms

Once diagnosed, antibiotics should be started almost immediately. Blood cultures (blood tests done to see if bacteria are present in the blood) are often done. If the infection is found to be bacterial, then antibiotic treatment will likely be started right away.

Depending on the severity, hospital admission or intensive care unit (ICU) admission may be needed. This is especially true if a person has hypoxia or difficulty breathing.

In the hospital, pulse oximetry is usually used to monitor oxygen levels continually via a small pulse oximeter device placed on the finger. Intravenous (IV) fluids may also be needed. If oxygen saturation is below 92% on oximetry, oxygen therapy may be needed, even this early in the infection.

When antibiotics are started promptly following early signs of infection, the fever may resolve within 48 to 72 hours.

Complications

The most common complication of early pneumonia (that may necessitate hospitalization) is a low oxygen level. Depending on the severity, oxygen supplementation may be needed, as well as admission to the ICU.

Red Hepatization

After the initial 24 hours, symptoms of pneumonia may worsen as red blood cells and other immune cells rush to the lungs and alveoli to fight the infection. This stage, known as red hepatization, occurs about two to three days after the infection develops.

As red blood cells fill the lungs, the lungs, which are normally pinkish-gray in color, literally become flushed with red. Reduced oxygen levels also cause the lungs to become dry and firm, much like a liver. The term "hepatization" refers to this liver-like appearance.

Symptoms

During red hepatization, symptoms are usually more severe even if treatment has been started. These can include:

• Coughing that produces thick, yellow-green, and sometimes blood-stained phlegm
• Fever, chills, and rigors (violent shivering)
• Severe shortness of breath
• Headache
• Muscle aches
• Cyanosis, in which the lips and fingers appear blue or even blackish due to low oxygen
• Extreme fatigue

In older adults, confusion or delirium may appear even despite oxygen therapy.

Managing/Treating Symptoms

During this stage of the infection, antibiotics are continued (intravenously if in the hospital) or started if a person has not yet been evaluated. For those diagnosed early, blood cultures may come back from the lab indicating the particular bacteria (if it is a bacterial pneumonia) responsible.

Knowing the type of bacteria present may lead physicians to change your treatment to a more appropriate or specific antibiotic. Sensitivities (tests that determine which antibiotic is most effective for the bacteria isolated) may also be returned and further guide appropriate therapy.

Oxygen may be started at this point or continued in those who already have low oxygen levels. In some cases, oxygen alone may be insufficient. A first step may be to use noninvasive positive pressure ventilation such as CPAP (continuous positive airway pressure). Positioning may also help, as lying in the prone position (on the stomach) can maximize the surface area of the lungs available to absorb oxygen.

If low oxygen levels persist, or if there is evidence that organs of the body are not getting enough oxygen (such as kidney dysfunction), insertion of an endotracheal tube and mechanical ventilation may be needed.

Additional testing may be needed if complications are suspected.

Complications

Complications may appear at any point with a diagnosis of pneumonia, but red hepatization is often when people appear most ill.

Bacteremia

Bacteria that are present in the lungs may spread in the bloodstream (bacteremia) and then travel to other regions of the body. With pneumococcal pneumonia, up to 25% to 30% of people will have bacteremia.

With bacteremia, bacteria can travel to and infect other bodily organs, including:

• The brain (meningitis)
• Heart valves (endocarditis)
• The lining of the heart (pericardium)
• Joints (septic arthritis)
• Kidneys
• Spleen

Septicemia and Sepsis

Septicemia, also called blood poisoning, may occur at any stage. While bacteremia refers to the presence of bacteria in the bloodstream, septicemia refers to a state in which bacteria are multiplying in the bloodstream. With septicemia, a person will appear extremely ill, often with a very rapid pulse and confusion.

In contrast to septicemia, sepsis refers to the body's response to bacteria in the bloodstream. This overwhelming response of the immune system is very critical. Even with medications to raise blood pressure (which is often very low) and counteract the intense inflammatory response, sepsis is often fatal. Significant research is focusing on ways to prevent sepsis from occurring.

Empyema

Since lobar pneumonia often extends to the lung lining (pleura), inflammation can result in the buildup of fluid between these membranes (a pleural effusion). In some cases, pus may build up and accumulate between the pleural membranes, a complication known as an empyema.

The most common causes include Streptococcus pneumoniae (the most common cause of bacterial pneumonia) and Staphylococcus. Symptoms are similar to pneumonia itself, with a cough, fever, chest pain, and shortness of breath, so doctors must be alert for this complication. If a significant pleural effusion is seen on imaging, further workup is often needed.

When an empyema is present, a thoracentesis is often the next step. This involves inserting a long, thin needle through the skin and into the pleural space to obtain a sample of the fluid. The sample can then be looked at in the lab to visualize any bacteria present and to do a culture of the fluid.

If a large empyema is present, a chest tube may need to be placed. This involves inserting a somewhat larger tube into the pleural space that is left in place and connected to continuous suction to remove the fluid.

In children and infants, especially those who have pneumonia due to Staphylococcus aureus, an empyema may occur. Severe infections may also result in the collapse of the lung (pneumothorax) and pneumatoceles (air-filled cysts within the lungs).

Grey Hepatization

The third stage of pneumonia, known as grey hepatization, sets in about four to six days after the infection develops. During this stage, red blood cells begin to break up, causing the lungs to become greyish-brown or yellow in color. The lungs will become drier, too, further taking on a liver-like consistency.

Symptoms

During grey hepatization, many of the same symptoms experienced in red hepatization will persist. Breathing may become especially difficult, necessitating additional oxygen therapy or mechanical ventilation. Fits of coughing may become more severe and produce blood.

Managing/Treating Symptoms

During grey hepatization, antibiotics (for bacterial pneumonia) will be continued. For those who are improving and in the hospital, intravenous antibiotics may be exchanged for oral antibiotics.

If complications have occurred, treatments to address these complications may continue, such as a chest tube to manage an empyema, and corticosteroids if an intense immune response is present.

Oxygen or other types of breathing assistance may continue, be stopped, or instead be initiated for the first time.

For those who are hospitalized, attention to other complications, such as dehydration, kidney dysfunction, and more, will require careful monitoring and management.

Complications

Complications noted in the earlier stages of pneumonia may not occur until grey hepatization for some people, especially those who have not received treatment.

For those who have a severe infection, a lung abscess may form.

In addition to symptoms associated with pneumonia—such as fever and cough—other symptoms of a lung abscess can include:

• An increase in sputum that can become foul-smelling
• Worsening of cough and fever, if they had been improving
• Night sweats (drenching sweats that require getting up and changing pajamas) can occur
• Weight loss in those who develop an abscess some time after their pneumonia occurred
• Coughing up blood (quite common)

An abscess itself can also lead to further complications, such as:

• An empyema (if not already present)
• A bronchopleural fistula (an abnormal passageway between the bronchi and the pleural cavity)
• Bleeding into the lungs

Treatment begins with broad-spectrum antibiotics (a lung abscess will usually require a change in antibiotics being used). If this is ineffective, the abscess may need to be drained (often with a long, narrow needle inserted through the skin).

In some cases, surgical removal of the abscess will be needed. Follow-up is also very important, as underlying lung cancer has been found in one to two out of 10 lung abscesses.

Resolution

The final stage of pneumonia, known as resolution, depends on how quickly treatment was started. Ordinarily, resolution of the infection occurs around eight days after the start of the infection.

In children, it can take two to three weeks for mild pneumonia to resolve, or up to eight weeks for pneumonia that is severe.

This recovery stage includes:

• Resolution of the infection
• Restoration of the normal airways and alveoli

At this point in the infection, the immune system works to repair the damage to the lungs. This includes the release of enzymes that break down damaged tissue so that it can be reabsorbed. An influx of cells called macrophages will travel through the lungs and "eat" (phagocytize) debris and white cells containing bacteria.

Leftover debris in the lungs that can't be eliminated in this way is usually coughed up.

Symptoms

Since debris in the lungs that can't otherwise be removed is coughed up, a cough productive of sputum is very common at this stage. Knowing that the body is continuing to repair damage that was done during the infection can help explain the fatigue often present (and why rest is still important).

If untreated (and in some cases even with treatment), respiratory symptoms may worsen, When treatment is started early, however, and no serious complications have occurred, symptoms usually improve significantly at this point in time (except for the cough).

If scar tissue develops in the pleura (pleural adhesions), pain with a deep breath may occur and may last for quite some time.

Managing/Treating Symptoms

Antibiotics are usually continued for at least 10 days. If antibiotics were previously given intravenously, they may be changed to oral tablets. For those who were hospitalized, many can be discharged (if not discharged already).

For those who continue to worsen, oxygen or mechanical ventilation may need to be started at this time. In some cases, oxygen therapy will be needed long-term. On the other hand, those who were on supplemental oxygen, but whose condition is improving, can start to be weaned off of oxygen therapy.

Complications

Complications discussed at other stages may occur later in the infection, especially lung abscesses.

The repair process may result in scar tissue in the lung linings (pleural adhesions) that may affect care in the future. For example, it could cause problems with pleural effusions or lung cancer surgery down the road.

Roughly 10% to 15% of people will have a recurrent episode of pneumonia within two years of the infection.

For some people, lung damage may persist, requiring long-term oxygen supplementation. Severe pneumonia may also worsen underlying chronic obstructive pulmonary disease (COPD).

Summary

Pneumonia, which can be viral or bacterial in origin, occurs in four stages: congestion, red hepatization, grey hepatization, and resolution. The names of each stage refer to how the infection affects the lungs. While congestion often manifests with flu-like symptoms, the hepatization stages tend to be marked by worsening breathing difficulties and a greater risk for complications.

The body works hard to repair the lungs during the resolution stage, but there may still be long-term lung damage. Many people with pneumonia require supplemental oxygen at various stages of the infection; for some, oxygen therapy will be needed long-term.