What Is Pneumonia: Symptoms, Causes, Treatments

Marion Sereti


December 24, 2022
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Pneumonia is an acute respiratory infection of the lungs that typically involves the alveoli1, the little sacks in our lungs.

When a healthy person breathes, the alveoli fill with air, allowing the exchange of oxygen and carbon dioxide. But when someone has pneumonia the alveoli are stuffed with pus and fluid, making breathing difficult and reducing oxygen intake. 

Pneumonia may affect one or both lungs. Its presentation can be roughly divided into two categories2:

  • Lobar pneumonia – Pneumonia that affects all or a large section of a lung
  • Bronchopneumonia (also called lobular pneumonia) – Pneumonia that affects patches of the lungs centres around the bronchi, the tubes that bring air into the lungs

Pneumonia can also be categorized based on how the infection is transmitted3:

  • Hospital-acquired pneumonia (HAP) –  This refers pneumonia acquired by someone during a hospital stay; it typically develops within 48 hours of hospitalization
  • Community-acquired pneumonia (CAP) – This is when someone has acquired pneumonia from the people around them and not in a hospital or within 48 hours of the hospital admission
  • Healthcare-associated pneumonia (HCAP) – This refers to pneumonia contracted after someone was recently hospitalized, was in a healthcare facility, such as a nursing home, dialysis center, or outpatient clinic, or received nursing care
  • Ventilator-associated pneumonia (VAP) – This form of pneumonia is normally acquired after using a ventilator and typically manifests 48 hours or longer after intubation (holding open the airway/trachea by placing a tube into the mouth or nose and subsequently into the airway)

Various infectious agents like bacteria, viruses, and fungi can cause pneumonia. It can cause mild to severe sickness in persons of all ages, but those with pre-existing health problems, who are over 65, or who are under five years old are particularly at risk. The World Health Organization (WHO) estimates that this disease is the single leading infectious cause of death in children globally, alone accounting for 15% of the deaths of cildren under the age of five in 20174

Bacterial Pneumonia

Bacterial pneumonia5 occurs when bacteria that cause pneumonia gather and grow in the lungs. It can develop independently or follow a viral cold or flu. As the lungs become infected, the alveoli swell and the immune system creates pus from killing the bacteria.

The most common causes of bacterial pneumonia are Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus.

Atypical Bacterial Pneumonia

Pneumonia caused by bacteria different to the more prevalent ones is called atypical pneumonia6. Despite the name, atypical pneumonia is not uncommon. 

In contrast to typical pneumonia, atypical pneumonia frequently demonstrates milder symptoms. This type of pneumonia, which often isn't severe enough to require bed rest, is known informally as "walking pneumonia.7"

According to the CDC, researchers typically label bacteria as "atypical" if they are challenging to find using standard bacterial procedures8. The bacteria that cause atypical pneumonia include:

  • Mycoplasma pneumoniae9
  • Chlamydia pneumoniae
  • Legionella pneumophila (also called Legionnaire’s disease)
  • Chlamydia psittaci (also called psittacosis)

Viral Pneumonia

Pneumonia is a collection of symptoms that can be caused by viruses that affect the upper respiratory tract, as well as the aforementioned bacteria. The majority of viral pneumonia is mild and passes faster than bacterial pneumonia10.

The most frequent causes of viral pneumonia in adults are SARS-CoV-2 (the virus that causes COVID-1911) and the influenza virus in boths adults12 and children13. In young children, respiratory syncytial virus (RSV) is the most frequent cause of viral pneumonia14.

Fungal Pneumonia

Funal pneumonia is not common but it does occur, Individuals with weak immune systems or chronic health conditions are more likely to get this type of pneumonia, as are those who have inhaled high concentrations of the microorganisms15. Depending on the region, the fungus that causes it can be found in soil, bird droppings, or in walls damaged during construction or rennovation.

The three most common fungi that cause fungal pneumonia are:

  • Pneumocystis 16 
  • Cryptococcus neoformans17
  • Aspergillus spp.18

Symptoms of Pneumonia

Pneumonia can present with mild to severe signs and symptoms, depending on your age, general health, and the type of infection that caused the illness.. Mild signs and symptoms frequently resemble cold or flu but linger longer.

Pneumonia symptoms and signs may include19:

  • Respiratory symptoms such as
    • Cough
    • Chest pains
    • Mucus (phlegm) production
    • Shortness of breath
  • Fatigue
  • Loss of appetite
  • Nausea/vomiting or diarrhea
  • Headaches
  • Fever/sweating/chills
  • Cyanosis – Bluish or gray color to the fingernails or lips20
  • Confusion, especially in older patients and those who are severely ill

It could be more difficult to identify a child's symptoms of pneumonia hence be on the lookout for additional symptoms such as2122:

  • Inability to feed or drink
  • Chest retractions/very heavy breathing
  • Unconsciousness
  • Hypothermia
  • Convulsions
A man coughing severely

Diagnosing Pneumonia

The diagnosis of pneumonia is typically based on your recent medical history (such as surgery, a cold, or travel exposures), a thorough examination, and some diagnostic tests. Your healthcare professional may also ask for risk factors, like23:

  • Lack of vaccinations
  • Current and/or long-term medications
  • Exposure to others with pneumonia
  • Recent travel destinations
  • Being around animals, particularly birds
  • Whether or not you smoke

During the physical examination, they will check your temperature and listen for any crackling in your lungs. The tests listed below could be carried out as part of the diagnosis24:

  • Blood tests – Checking the levels of certain things in your blood lets the medical practitioner know if your body is fighting an infection or not
  • Pulse oximetry test – This tests the level of oxygen in your blood through a clip placed on your finger; if you have pneumonia, this will be lower than normal
  • Chest x-ray – This is the basic scanning test to detect for abnormalities in the lungs
  • Lung ultrasound – This is another bed-side test like a chest x-ray to detect lung abnormalities25
  • CT scan – If the chest x-ray and lung ultrasounds are unclear, a CT scan may be performed for a more detailed and accurate examination26; it is more in-depth and requires being moved from the bed to a big machine
  • Sputum or blood culture, or a PCR test – Using a sample of spit, mucus, and/or blood, the medical practitioners can culture the germs that have made you sick to find out what type they are
  • Needle thoracostomy – This is another way of getting a sample for testing, specifically from the space between your lungs and chest wall; this is called a pleural fluid sample
  • Bronchoscopy – This is where a thin tube with a light and a camera is inserted down your throat to see what is happening in your lungs

Differentiating pneumonia from other lung disorders, especially in patients with co-existing pulmonary disease, can be a very dire task; therefore, always give your doctor all information about your medical history.

Transmission and Risk Factors of Pneumonia

Pneumonia is contagious in some cases – it can spread from person to person. People with pneumonia typically spread the disease by coughing, sneezing, or talking, all of which release respiratory droplets into the air. Close contacts may then breathe in these droplets, which carry the bacteria, virus, or fungus that caused the pneumonia

While almost anyone can get pneumonia, the following groups of people are more susceptible to developing pneumonia:

  • Infants and young children whose immune systems have not fully matured (under two years old or younger)
  • Elderly individuals with weak immune systems
  • Persons suffering from immune-compromising conditions like cancer, HIV, and AIDS
  • Expectant mothers
  • Persons with lung and respiratory disorders such as asthma, cystic fibrosis, and chronic obstructive pulmonary disease (COPD)
  • Individuals receiving immune system-suppressing drugs
  • Individuals who suffer from autoimmune conditions like rheumatoid arthritis
  • Individuals recovering from surgery
  • Smokers

Therefore, pneumonia-prone individuals should exercise extra caution while interacting with others who have recently recovered from the illness.

A woman talking to her doctor


The treatment plan for pneumonia will depend on the severity of the symptoms and the underlying infection. In severe cases of pneumonia that you need hospital treatment, you might receive intravenous fluids, antibiotics, oxygen therapy, and possibly additional breathing treatments.

If your pneumonia is not sever enough to require hospitalization, then, depending on the specific cause of your pneumonia, you may receive a prescription. If necessary, your doctor may also advise using over-the-counter (OTC) drugs to treat your discomfort and or other symptoms. Additionally, you might try certain lifestyle changes and adapt while you're recovering.

Treatments can include:


Bacterial pneumonia is typically treated using antibiotics, such as penicillin. 

Antiobiotics are only useful for treating bacterial pneumonia, as they do nothing to combat viruses or fungi. Taking antibiotics when you have a non-bacterial infection, or not finishing the course of antibiotics prescribed to you, contributes to the development of antibiotic resistant bacteria. This makes it harder to treat bacterial infections in the future27.

Cough Medicine

You can use cough medication to relieve your pneumonic cough so that you can get some rest. It's a good idea to take some because it helps to loosen and move mucus from your lungs. 

However, relatively few studies have examined whether over-the-counter cough medications reduce coughing brought on by pneumonia. Also, the FDA suggests28 avoiding OTC cough medications for children younger than 2 years of age.

Pain Killers

You can take pain relievers as needed for pain and fever. These include acetaminophen (also known at paracetamol, often under the brand name Tylenol), aspirin, and ibuprofen (often under the brand names Advil and Motrin IB). Reducing your pain and fever will help you sleep better and recover more. There is some evidence that ibuprofen is a more effective pain killer and fever reducer than acetaminophen29

However, you should not take ibuprofen and aspirin at the same time, as their interaction increases the risk of bleeding in your digestive tract30. If you take aspirin regularly for its beneficial cardiovascular effects, discuss alternative pain killers with you doctors, as there are plenty that exist that do not interact with aspirin31.

Antifungal Medicines

Antifungal medicines are the primary treatment option for fungal pneumonia32. The particular instance and type of infection affect the precise dosages and administration techniques. Varieties of antifungal medication that you may be prescribed include itraconazole (may be under the brand name Onmel or Sporadox), fluconazole (often under the brande name Diflucan), amphotericin B (often under the brand name Fungizone or Amphocin), and ketoconazole (often under the brand name Nizoral)33..


In the World Health Organization’s fact sheet for pneumonia, it is stated that it can be prevented by getting vaccinated, eating a healthy diet, and addressing environmental issues. 


Not all cases of pneumonia cannot be prevented by vaccination. However, pneumococcus and flu-caused pneumonia can both be prevented with vaccinations. After the introduction of the pneumococcus vaccine, countries reported a reduction in pneumonia deaths of up to 70%34. In addition, those who are vaccinated before they contract pneumonia frequently exhibit:

  • Fewer significant problems
  • Less severe infections
  • A shorter duration

Given there are multiple causes of pneumonia, there are multple vaccines that are reccomended to prevent it. The following vaccines are the most effective way to prevent pneumonia35:

  • Pneumococcus (PCV)
  • Flu (influenza)
  • Hib (Haemophilus influenzae type b)
  • Measles 
  • Whooping cough (pertussis) 

Behavioral/Environmental Changes

Practicing good hygiene is another way to prevent pneumonia. The CDC suggests some specific measures such as36:

  • Routinely washing your hands
  • Cleaning and sanitizing frequently handled surfaces
  • Sneezing or coughing into your elbow, sleeve, or a tissue
  • Reducing exposure to cigarette smoke and/or giving up smoking
  • Treating medical disorders with care (like asthma, diabetes, or heart disease)

Such behaviors are particularly important if you are in a crowded area, such as a home with many people in37. The World Health Organization also recommends making enviromental changes that reduce indoor air pollution, such as reducing or eliminating smoke-producing fires and stoves38.


Most people who contract pneumonia receive treatment and recover, feeling better. However, even with the finest treatment, severe pneumonia can be quite deadly. The population most at risk for developing severe or deadly pneumonia is the elderly or those with underlying health issues.

If you suspect you or a loved one may have pneumonia, don't hesitate to seek medical attention. Keep track of your symptoms, know what vaccinations you’ve had, and be aware of your environment because, together, these will lessen the burden of pneumonia.

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