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There are various causes of pneumonia, namely, different viruses, bacteria, and fungi. In the United States, viral pneumonia occurs primarily because of influenza, respiratory syncytial virus (RSV), and SARS-CoV-2.

The most common cause of bacterial pneumonia is Streptococcus pneumoniae (pneumococcus). Nevertheless, doctors cannot determine precisely which germ amongst these causes pneumonia to occur.

There are other environmental risk factors of pneumonia too. Patients can develop community-acquired pneumonia when someone within their community gets pneumonia – where the community does not imply a hospital setting.

Community-Acquired Pneumonia

  • Streptococcus pneumonia
  •  Streptococcus pyogenes
  • Haemophilus influenzae
  • Klebsiella pneumoniae
  • Mycoplasma pneumonia and Legionella pneumophila (tend to occur in epidemics)
  • Staphylococcus aureus (in children after a viral illness like measles, in people with diabetes, or the elderly during ‘flu’ epidemics)

On the other hand, healthcare-associated pneumonia occurs when someone gets pneumonia during or after a stay in a hospital, long-term care facility, or dialysis center.

Hospital-Acquired Pneumonia

  • Gram-negative bacteria e.g. Pseudomonas aeruginosa
  • MRSA (Methicillin-resistant)
  • VRSA (Vancomycin-resistant)
  • Staphylococcus aureus

The third is ventilator-associated pneumonia which occurs when someone gets the disease after being on a ventilator. In each of these situations, the germs are different.

Aspiration Pneumonia

  • Anaerobic and gram-negative organisms (associated with aspiration, e.g., stroke, seizures, unconsciousness).


The main types of pneumonia are:

  • Bacterial Pneumonia: This is caused by different bacterias, the most common one being streptococcus pneumoniae. This occurs when the body is weak in any regard due to illness, old age, poor immunity, and nutrition, and the bacteria can find their way into the lungs. This type can afflict everyone, but people who smoke, drink, have a weak immune system or have had recent surgery are especially at risk.
  • Viral Pneumonia: caused by different viruses, including the influenza virus. About ⅓ rd of the total cases occur because of this. You are more likely to get bacterial pneumonia if you have viral pneumonia.
  • Mycoplasma Pneumonia: This one has signs and symptoms which are somewhat different from other types. It is also called atypical pneumonia caused by the bacterium Mycoplasma pneumoniae. This one leads to a mild but widely spread pneumonia which can afflict all age groups.
  • Other Pneumonia: These are less common but can be caused by infections, including fungi.

Signs and Symptoms

The symptoms of Pneumonia can vary from being barely noticeable to being so severe that the patient needs to be hospitalized. The body's response to Pneumonia mainly depends on the cause of Pneumonia and the age and overall health of the afflicted person.

In general, signs and symptoms include:

  • Bluish color of the lips and fingernails
  • Confused mental state, especially in older people
  • Coughing that produces green, yellow, or bloody mucus
  • Fever
  • Profuse sweating
  • Loss of appetite
  • Low energy and severe exhaustion
  • Accelerated breathing
  • Rapid pulse
  • Shaking chills
  • Sharp or dull chest pain that increases in intensity with deep breaths or coughing

Symptoms of viral pneumonia also include:

  • Headache
  • Increasing shortness of breath
  • Muscle pain
  • Weakness
  • Worsening of the cough

Symptoms of Mycoplasma Pneumonia include a severe cough that also produces mucus, amongst other symptoms.

Risk Factors

While anyone can get pneumonia, some age groups are at higher risk of affliction than others, such as:

  • Newborns to two-year-olds.
  • People aged 65 and above.
  • Those with weakened immune systems because of previous conditions and medications like cancer drugs.
  • People who have chronic medical conditions like diabetes and asthma.
  • People who have recently had a cold or flu.
  • People who have been hospitalized or were on a ventilator.
  • People who have had a stroke, issues swallowing, or some immobility.
  • People who smoke, drink, use drugs, or are even regularly exposed to lung irritants.


Diagnosis of pneumonia is based on the patient's recent health history, like a recent cold, surgery, or exposure during travel. The doctor can diagnose after following up on the patient’s record. Sometimes, they use tests to confirm the diagnosis, such as:

  • Blood tests to see if the infection is present and has spread to the bloodstream. Arterial blood gas testing can also check how much oxygen is present in the blood.
  • Complete Blood Count (CBC)
  • C-Reactive protein
  • ESR 
  • Mycoplasma Pneumonia Antibodies
  • Blood Culture and sensitivity
  • Chest X-ray to evaluate the lungs and their components.
  • Sputum cultures
  • Pulse Oximetry
  • CT scan

Differential Diagnosis

Pneumonia has to be differentiated from other conditions with similar symptoms such as cough, fever, shortness of breath, and tachypnoea, as seen in asthma, COPD, CHF, cancer, GERD, and pulmonary emboli.


In general, people respond well to treatment, but the condition can be severe and even lethal. Post-treatment complications are more common for at-risk patients. Complications include:

  • Pleural effusion
  • Lung abscess 
  • Empyema
  • Pericardial effusion/pericarditis
  • Pneumothorax, particularly Staph. aureus infection, Pneumocystis jiroveci pneumonia
  • Meningitis
  • Septicemia with multi-organ failure
  • Adult respiratory distress syndrome (ARDS)


When you've been diagnosed with pneumonia, your doctor will work with you to create a treatment plan. The type of pneumonia you have, how sick you are, your age, and whether you have any other health problems all influence your treatment options. The treatment's goals are to eliminate the infection and prevent complications. It's important to adhere to your treatment plan until you've fully recovered.

Take the medications that your doctor has prescribed. You will be given an antibiotic if bacteria cause your pneumonia. Even though you will most likely start to feel better in a couple of days, it is essential to finish the antibiotic course. Antibiotics are ineffective against viruses. Your doctor may prescribe antiviral medicine if you have viral pneumonia. Symptom management and rest are sometimes all that is required.


Medications used for bacterial pneumonia are antibiotics. Antibiotics such as amoxicillin, doxycycline, clarithromycin are usually used to treat community-acquired pneumonia and other exceptional cases. Third- and fourth-generation cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and vancomycin are all recommended for hospital-acquired pneumonia. Clindamycin, a combination of a beta-lactam antibiotic plus metronidazole, or aminoglycoside, is typical for aspiration pneumonia. Corticosteroids are sometimes utilized for aspiration pneumonia, although limited data support their effectiveness. Neuraminidase inhibitors may treat viral pneumonia caused by influenza viruses (influenza A and B). No specific antiviral drugs are advised for other forms of community-acquired viral pneumonia caused by SARS coronavirus, adenovirus, adenovirus, hantavirus, and parainfluenza virus. Rimantadine or amantadine can be used to treat influenza A. In contrast, oseltamivir, zanamivir, or peramivir can be used to treat influenza B. Antifungal medicines are used to treat fungal variations.


Flu Vaccine: A case of the flu can lead to bacterial pneumonia. You can lower your risk by taking a flu shot every year.

Pneumococcal Vaccine: Prevent pneumonia caused by pneumococcal bacteria by getting the pneumococcal vaccine such as Prevnar 13 and Pneumovax 23

Hand Hygiene: Wash your hands frequently with soap and water or an alcohol-based hand sanitizer to maintain healthy hygiene.

Don't Smoke: Smoking harms your lungs and makes it difficult for your body to fight viruses and sickness. If you smoke, consult with your primary care physician about quitting as soon as possible.

Healthy Lifestyle: Eat a well-balanced diet rich in fruits and vegetables to live a healthy lifestyle. Exercise regularly and make sure you get enough rest for a healthy immune system.

Avoid Sick People: Being around ill people increases your chances of acquiring the disease.

Our clinical experts continually monitor the health and medical content posted on CURA4U, and we update our blogs and articles when new information becomes available. Last reviewed by Dr.Saad Zia on May 27, 2023.


Pneumonia Symptoms and Diagnosis | American Lung Association


Pneumonia - What Is Pneumonia? | NHLBI, NIH


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