What are the 4 Stages of Pneumonia: Best 101 Guide

Want to know what are the 4 stages of pneumonia1? Keep reading to find out more.

Pneumonia is a disease that often flies under the public’s radar and even the global health community. It kills more children under five years old every year than AIDS, malaria, and measles combined.”

–Mandy Moore

1. What Is Pneumonia?

Pneumonia is a contagious infection that usually affects one lung and parts. This serious infection can be bacterial, viral, or fungal.

The infection causes inflammation in the alveoli2 (or air sac). Air sacs are tiny sacs present in the lungs that help in breathing.

During pneumonia, these alveoli fill them with pus, blood cells, and other infectious fluid and become inflamed, which causes difficulty breathing.

Humans have two lungs – a left lung and a right lung. These lungs are affected by pneumonia, commonly known as Bronchial pneumonia3 or Bronchopneumonia.

Three lobes are present in the lungs; if one or more lobes get affected, we recognize it as Lobar pneumonia. It’s a kind of acute bacterial infection.

Pneumonia can cause illness in young children aged 1 to 5, older adults (above 65), and people having other health problems. According to UNICEF reports, pneumonia is the most infectious killer disease for children aged 5.

It claims a child dies due to pneumonia every 39 seconds, and all of these losses can be preventable.

Same as UNICEF, WHO also claims that 14% of children under the age of 5 died due to pneumonia in 2019

2. Symptoms

pneumonia symptoms in adults

Before we go into what are the 4 stages of pneumonia, let us talk about its symptoms. The symptoms of pneumonia4 include:-

  • Cough (with green, yellow, or bloody phlegm/pus),
  • Fever and chills with shaking,
  • Difficulty in breathing,
  • Rapid breathing
  • Nausea and vomiting,
  • Weakness or low energy level,
  • Rapid heartbeat,
  • Weakened immune systems,
  • Sweating,
  • Chest pain,
  • Loss of appetite,
  • Mental confusion (in older adults above 65)

A patient may have a high fever in case of bacterial infection and blue lips or nails due to insufficient oxygen levels in the body.

A person suffering from viral pneumonia shows the same symptoms as influenza, including fever, headaches, chest pain, body aches, low energy level, cough without sputum, chills, and difficulty breathing and swallowing.

If you suspect these common symptoms, see your doctor immediately before they worsen. It can increase the risk of death if not treated on time.

3. Causes

What causes Pneumonia? | #aumsum #kids #science #education #children

The most common infection-causing agents for pneumonia, including viruses, bacteria, and fungi, are:-

  • Streptococcus pneumonia (a common cause of bacterial pneumonia usually found in children worldwide)
  • Haemophilus influenza5 (2nd most common bacterial cause)
  • Chlamydia pneumonia
  • respiratory syncytial virus (a common cause of viral pneumonia)
  • Rhinoviruses
  • Pneumocystis jirovec (newborns who are infected with HIV)
  • Staphylococcus aureus

4. Transmission

Pneumonia-transmitting viruses6 and bacteria are most commonly found in the nose or throat and can cause infection in the lungs if inhaled. Airborne droplets can also easily transmit it through coughing or sneezing.

In addition, it can be transmitted through blood during childbirth. There’s a need to research more about the other pathogens that can cause pneumonia and other ways to get transmitted.

5. What are the 4 Stages Of Pneumonia?

Pneumonia - Stages of pneumonia

5.1. Stage 1: Congestion

Congestion comes first in the list. This first stage occurs within 24 hours after contracting pneumonia.

The lungs become heavy and red during the congestion phase due to increased blood flow. Capillaries in alveolar walls become swallowed, and the infection spreads all over.

A person may experience coughing, trouble breathing, fatigue, loss of appetite, and heaviness in the chest as early symptoms of pneumonia during this stage.

5.2. Stage 2: Red Hepatization

Then comes Red Hepatization within 2 to 3 days of contracting pneumonia.

Red blood cells, WBCs, and other immune cells enter the lungs to fight infection during this stage. The affected lungs will become red, firm, dry, scar tissue, granular and airless, resembling the liver.

The lung airways and alveoli will be clogged due to red blood cells, white blood cells, and cellular debris, which increases the number of bacteria.

Although the immune cells fight the infection during this stage, people may experience symptoms like- Shortness of breath, body or muscle aches, cough, headache, fatigue, chills and fever, sweating, chest pain, blue nails, and lips due to insufficient levels of oxygen in the blood.

Older adults above 65 years may experience mental confusion and retardation during this phase.

5.3. Stage 3:Gray Hepatization 

Gray Hepatization7 comes third. This third stage occurs within 2-3 days after red hepatization (stage 2).

The lungs will give a greyish or yellow appearance of decay of red blood cells and other immune cells. The lungs will look to be more pale and dry than usual.

However, immune cells remain, and symptoms will likely persist.

5.4. Stage 4: Resolutions

Resolution is the complete recovery phase and final stage (7-10 days).

In this, inflammatory fluids and cellular debris are reabsorbed, and the normal airways and alveolars are restored.

Macrophages 8help to clear leftover debris; people may develop a productive cough that helps to remove fluid from the lungs.

6. Diagnosis

Doctors Epidemiologists examine x-ray for pneumonia of a Covid-19 patient.
From UnlimPhotos

After discussing what are the 4 stages of Pneumonia and how it spreads, let us talk about how pneumonia can be diagnosed.

Pneumonia diagnosis starts only after your doctor asks about your medical history and physical exam.

The doctor will use a stethoscope to listen to your lungs to observe abnormal bubbling and crackling sounds during inhalation and exhalation.

If any signs suspect pneumonia, your doctor may recommend the following tests to confirm pneumonia, that includes: –

  1. Blood tests (used to detect infection and causing agent) like-
    • Polymerase chain reaction or PCR
    • Influenza
    • Covid-19
  2. Chest X-ray (helps to identify the location of infection)
  3. Pulse oximetry (helps to measure the amount of oxygen present in the blood)
  4. Sputum test (fluid from the lungs, helps to find the infection cause)
  5. Arterial Blood test (helps to measure the oxygen level in the blood from an artery)
  6. Bronchoscopy (used to check airways)

If you are above 65 years, then your doctor may recommend some additional tests, including; –

  1. Computerized Tomography or CT Scan (to get a detailed image of the lungs)
  2. Pleural fluid culture (sample taken from pleural area of ribs, help to determine the type of infection)

7. Treatment Of Pneumonia

What are the 4 stages of pneumonia
Photo by Mikhail Nilov on Pexels

Treatment of pneumonia will depend on the type of pneumonia and its causative agents, at which stage the patient is suffering, and their age, medical history, and illnesses.

For bacterial pneumonia, antibiotics can be used.

However, in the case of viral pneumonia, antibiotics may not work effectively. Patients suffering from this are generally treated with antivirals and supportive care such as getting rest, plenty of water, warm drinks and beverages, steam bathing, quitting smoking or hookahs, etc.

Always consult your doctor before taking any medicine.

Senior citizens who experience many other health issues or show severe pneumonia-like symptoms may need to be hospitalized in several cases. The treatments that may be included in hospitals according to signs of serious complications are:-

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

8. Complications Of Pneumonia

Why is pneumonia so dangerous? - Eve Gaus and Vanessa Ruiz

A healthy person can fight against the infection with their natural immunity; serious complications of pneumonia mostly occur in young children (1-5 years), older adults (above 65), people whose immune systems are compromised, and people who are suffering from other chronic diseases like diabetes.

  • The most common complications of pneumonia include:-
  • Failure of the respiratory system
  • Acute respiratory distress syndrome
  • Sepsis
  • Lung abscesses

Children’s immune systems can be weakened by a lack of nutrition (malnutrition), and symptomatic HIV 9and measles in babies can increase the risk of pneumonia.

Environmental factors are also responsible for a child’s susceptibility to pneumonia, such as indoor air pollution, overcrowded houses, parental smoking, etc.

Is Pneumonia Contagious?

During the initial period, pneumonia is not very infectious. Still, after some time, causative agents or germs of pneumonia become contagious or can easily spread through coughs or sneezes, and also can be spread by contaminated surfaces.

It can be transferred to the child during birth through body fluids like blood.

9. Prevention

Pneumonia can be prevented by following the preventive measures such as:-

  • Get vaccinated (Hib vaccine for children)
  • adequate nutrition
  • following good hygiene
  • Proper handwashing with soap (at least 20 seconds) can reduce the risk of pneumonia
  • quit smoking
  • Take a healthy diet
  • regular exercise
  • adequate sleep
  • plenty of water

In the case of children, preventive measures are the HIV vaccine to reduce child mortality rate, adequate nutrition to build a strong immune system, proper breastfeeding for at least 6 6months, combatting environmental factors like indoor pollution, and maintaining hygiene in packed houses at risk of pneumonia infection.

10. Frequently Asked Questions (FAQs)

10.1. What is the danger level of pneumonia?

Pneumonia can be fatal and can be quite serious. Respiratory failure, sepsis, and lung abscess are among the complications from pneumonia that older adults, children, those with compromised immune systems, and those with other health issues are more prone to experience. Healthy lifestyles and habits can help prevent pneumonia.

10.2. Can you cure pneumonia at home?

No, home cures will not be able to treat or cure pneumonia, which is a dangerous condition. However getting adequate sleep, consuming warm liquids like ginger or fenugreek tea, and following other advice may help control discomfort.


Talking about lobar pneumonia and its stages and complications can be frightening, but one should not take it lightly.

However, with proper and effective treatment, most people will recover from it. So, you must make sure that your treatment should start as soon as possible.

Hopefully, now you have a better understanding of pneumonia; its stages, symptoms, causes, treatment, and how it will get transmitted.

So that’s all we need to keep you up to date with pneumonia. If you have any queries about this topic, please comment below. Thank you, and have a wonderful day!

  1. Hendriks, Simone A., et al. “Pneumonia, Intake Problems, and Survival Among Nursing Home Residents With Variable Stages of Dementia in the Netherlands.” Alzheimer Disease & Associated Disorders 31.3 (2017): 200-208. ↩︎
  2. Chao, Jie, John G. Wood, and Norberto C. Gonzalez. “Alveolar hypoxia, alveolar macrophages, and systemic inflammation.” Respiratory research 10 (2009): 1-8. ↩︎
  3. Zhu, Xiao-Hua, et al. “Clinical analysis of immune function changes in children with bronchial pneumonia.” Zhongguo Dang dai er ke za zhi= Chinese Journal of Contemporary Pediatrics 15.3 (2013): 175-178. ↩︎
  4. Melbye, Hasse, et al. “Diagnosis of pneumonia in adults in general practice relative importance of typical symptoms and abnormal chest signs evaluated against a radiographic reference standard.” Scandinavian journal of primary health care 10.3 (1992): 226-233. ↩︎
  5. Turk, D. C. “The pathogenicity of Haemophilus influenzae.” Journal of medical microbiology 18.1 (1984): 1-16. ↩︎
  6. Saba, Sumayea Kabir, et al. “Updates on COVID-19: Virology, Etiology, Epidemiology, Pathogenesis, Diagnosis, Transmission and Prevention.” Bangladesh Pharmaceutical Journal 25.2 (2022): 143-163. ↩︎
  7. Zubair, R., A. M. Z. Khan, and M. A. Sabri. “Pathology in camel lungs.” J. Camel Sci 1.1 (2004): 103-106. ↩︎
  8. Gordon, Siamon. “Alternative activation of macrophages.” Nature reviews immunology 3.1 (2003): 23-35. ↩︎
  9. Henrard, Denis R., et al. “Virologic and immunologic characterization of symptomatic and asymptomatic primary HIV-1 infection.” JAIDS Journal of Acquired Immune Deficiency Syndromes 9.3 (1995): 305-310. ↩︎

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Sarita Kapoor

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