Pneumonia is a lung infection that can cause cough, difficulty breathing, and fever. Pneumonia may affect one or both lungs, and can cause serious illness in young children, people over age 65, and those who have other underlying health problems.
Early signs of pneumonia may include:
- Cough
- May produce phlegm or mucus that may be yellow, greenish, or bloody
- Shortness of breath
- Fever
- Chills
- Shaking
- Feeling unwell (malaise)
- Sharp pain on inhalation or when coughing
- Coughing up blood (occasionally)
Other signs and symptoms of pneumonia may include:
- Difficulty breathing
- Sweating
- Fast heartbeat
- Loss of appetite
- Fatigue
- Loss of energy
- Nausea and vomiting (more common in young children)
- Confusion (more common in older people)
How Do You Get Pneumonia?
Common causes of pneumonia include bacteria, viruses, and fungi.
Typical bacteria that cause pneumonia include:
- S. pneumoniae (most common bacterial cause)
- Haemophilus influenzae
- Moraxella catarrhalis
- Staphylococcus aureus
- Group A streptococci
- Aerobic gram-negative bacteria (e.g., Enterobacteriaceae such as Klebsiella spp or Escherichia coli)
- Microaerophilic bacteria and anaerobes (associated with aspiration)
Atypical bacteria that cause pneumonia include:
- Legionella spp
- Mycoplasma pneumoniae
- Chlamydia pneumoniae
- Chlamydia psittaci
- Coxiella burnetii
Respiratory viruses that cause pneumonia include:
- Influenza (“flu”) A and B viruses
- Coronaviruses (e.g., COVID-19, Middle East respiratory syndrome coronavirus)
- Rhinoviruses
- Adenoviruses
- Parainfluenza viruses
- Respiratory syncytial virus (RSV)
- Human metapneumovirus
- Human bocaviruses
How Is Pneumonia Diagnosed?
Pneumonia is diagnosed with a patient history and physical examination. The physical exam consists of a doctor listening to the lungs with a stethoscope for crackling, bubbling, and rumbling sounds on inhalation.
Tests to confirm pneumonia include:
- Blood or body fluid tests
- Influenza
- COVID-19
- Polymerase chain reaction (PCR)
- Sputum test on a sample of mucus (sputum) taken after a deep cough
- Chest X-ray
- Pulse oximetry to measure blood oxygen levels
- Arterial blood gas test
- Urinary antigen testing for S. pneumoniae
- Computerized tomography (CT) scan of the chest
- Pleural fluid culture
- Bronchoscopy
What Is the Treatment for Pneumonia?
Pneumonia treatment depends on the type of pneumonia, how sick the patient is, the patient’s age, and if other underlying medical conditions are present.
Mild cases of pneumonia may go away own their own with adequate rest and symptom management. Home treatment for pneumonia may include:
- Getting plenty of rest
- Drinking adequate fluids
- Steamy baths or showers or use of a humidifier can help open airways
- Fever reducers
- Nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin) or naproxen (Aleve)
- Acetaminophen (Tylenol)
- Aspirin
- Do not give aspirin to children due to the risk of a serious condition called Reye’s syndrome
- Don’t smoke and avoid secondhand smoke or any other lung irritants
- Check with your doctor before taking cough medicines because coughing helps the body work to rid itself of infection
If medicines are needed, medications used to treat pneumonia include:
- Antibiotics, if the cause is bacterial
- Antivirals, if the cause is viral
Hospitalization may be indicated in severe cases of pneumonia and treatment may include:
- Breathing treatments
- Intravenous (IV) fluids
- Intravenous antibiotics
- Oxygen therapy
From 
https://www.uptodate.com/contents/pneumonia-in-adults-the-basics?search=pneumonia%20stages&source=search_result&selectedTitle=3~150&usage_type=default&display_rank=3
https://www.uptodate.com/contents/overview-of-community-acquired-pneumonia-in-adults?search=pneumonia%20causes&source=search_result&selectedTitle=3~150&usage_type=default&display_rank=3#H3873548286
https://www.lung.org/lung-health-diseases/lung-disease-lookup/pneumonia?referrer=https://www.google.com/
https://radiopaedia.org/articles/lobar-pneumonia?lang=us