Is Pneumonia Contagious?

Pneumonia has always been a very common infection among the people across the various continents. With many types of itself and each of them caused by a multitude of organisms, the varying degrees of infections and other problems it can create, and further the complications that occur, it is hugely important to understand the disease and its details.

For the ease of understanding, it is easier to be explained in form of FAQ.

Q. How to know more about Pneumonia?

To understand what Pneumonia is, we need to know what lung is. The most important resource to maintain life is Oxygen that we breathe. Without Oxygen all of our cells die very fast. Most importantly, brain starts to die of lack of oxygen within around 6 minutes. And you know, we always use the term ‘Brain Dead’ to imply actual death.

Q. Can you please explain about how the lungs function?

Lungs are in fact, two inflatable bags in both sides of our chest cavity, right and left. These bags are connected to the outside world through the nose and mouth, which communicates with a single central tube, Trachea. The trachea divides into left and right bronchus, which is further divided into bronchioles. At the end of the bronchioles there are small air bags called as alveoli. Here, the exchange of air takes place. [2, 3]

The airway division inside the lungs. Trachea, bronchus, bronchioles, and alveoli can be seen PICTURE image

Image 1: The airway division inside the lungs. Trachea, bronchus, bronchioles, and alveoli can be seen. [1]

How breathing occurs is absolutely amazing. The diaphragm, which is controlled by the brain contracts, which in turn pulls the lung downwards creating a negative pressure inside the chest cavity. This causes air to flow inside to the lungs. Once air reaches the alveoli, there is passage of oxygen from alveoli to the small blood vessels (capillaries) that pass through.

In the capillaries, the red blood cells will release CO2 which they obtained from various tissues and take up the O2 which they received from the alveoli. Now they can travel throughout the body to distribute O2 to all other tissues. Whereas, the CO2 released in the capillaries near to the alveoli will pass to the alveoli and will be released back into air when the person exhales.[2, 3]

Q. So how does this connect to pneumonia?

‘Pneumonia’ the word itself is relating to the lung. ‘Pneumon’ in Greek meant ‘Lung’. When there is an infection or inflammation of the lung tissue, with collection of pus or fluid in the alveoli, then it is called as pneumonia. [4, 5]

difference between a normal alveoli and pus filled alveoli in pneumonia.

Image 2: Image showing the difference between a normal alveoli and pus filled alveoli in pneumonia. [6]

Q. What are the Symptoms of Pneumonia?

When there is inflammation and pus in the alveoli, it is going to cause a lot of discomfort with symptoms. Usually what we see are

  • Fever[8, 9]
  • Cough with sputum [8, 9]
  • Weakness[8, 9]
  • Chest Pain[8, 9]
  • Breathing difficulty[8, 9]
  • Increased rate of breathing[7, 8, 9]

When certain symptoms like increased effort to breath is seen in children or in elderly individuals, it is important for them to get immediate medical attention.

Q. Why does pneumonia occur or what are the causes of pneumonia?

Pneumonia can be caused by infective agents or non-infectious agents. When the infective agents are obtained from our normal living environment, we call it a ‘Community Acquired Pneumonia’. If the infective agent spreads to a person from a hospital setting, then we call it as ‘Hospital Acquired Pneumonia’ or ’Nosocomial Pneumonia’.

Infective agents

Bacteria- [10, 11, 12]

  • Streptococcus pneumonia
  • Hemophilus influenza
  • Chlamydophila pneumonia
  • Mycoplasma pneumonia
  • Chlamydia psittaci
  • Staphylococcus aureus
  • Moraxella catarrhalis
  • Legionella pneumophila
  • Pseudomona aeruginosa
  • Coxiella burnetti

Virus [13][14]

  • Corona viruses
  • Influenza virus
  • Respiratory syncytial virus
  • Adenovirus
  • Parainfluenza
  • Cytomegalovirus

Fungus[15, 16]

  • Histoplasma capsulatum
  • Blastomyces dermatitidis
  • Coccidioides immitis
  • Paracoccidioides brasiliensis
  • Cryptococcus neoformans
  • Pneumocystis jiroveci

Parasites [14]

  • Toxoplasma gondii
  • Strongyloides stercoralis
  • Ascaris lumbricoides
  • Ankylostoma duodenale
  • Paragonimus westermanii

Non- infectious

  • Diffuse alveolar damage
  • Organizing pneumonia
  • Nonspecific interstitial pneumonia
  • Lymphocytic interstitial pneumonia
  • Desquamative interstitial pneumonia
  • Respiratory bronchiolitis interstitial lung disease
  • Interstitial pneumonia[17, 18]

Other types of pneumonia we see is

  • Aspiration pneumonia – Occurs due to aspiration of food, fluid, vomitus, chemicals
  • Walking pneumonia – It is a simple pneumonia caused by Mycoplasma pneumoniae

Q. Is pneumonia a deadly disease?

It is not a problem in the general population and gets stabilized within 3-6 days [19]. But, in young children and elderly people, the mortality is high if appropriate treatment is not given in time.

Mortality can be as high as 30%-50% in those patients who require intensive care.[11] Severity is increased at the extremes of age or with other diseases existing along with pneumonia in the same person[11]. Pneumonia is the most common hospital acquired infection that causes death.[14]

Q. How do we diagnose pneumonia?

Diagnosis is based on the symptoms, the findings on examination and the investigations which would be done. The usual investigations that we do are

  • Complete blood count (CBC) – Will show an increased number of WBC.
  • Serum electrolytes
  • C- reactive protein
  • Sputum for Microscopy and culture- Identification of the organism
  • Blood for culture[21]
  • Chest X-ray [20] – Location and extend of the infection can be seen. Further, we can also see if any associated fluid collection (Pleural effusion) is present in the pleural space.
  • Pleural fluid can be drained and sent for microscopy and culture.

Image 3: An X-ray film showing Pneumonia of the right lower lobe

Q. Is Pneumonia contagious?

Pneumonia in infective conditions especially those due to bacteria or viruses can be contagious. Fungal and parasitic pneumonias are generally less frequently diagnosed and they are less contagious too.

Q. Is pneumonia contagious to babies?

Yes, pneumonia can spread to babies or infants more easily than in adults. This is because their immunity levels are lower and are easily susceptible to any infections.

Q. How does pneumonia become contagious or how does pneumonia spread from person to person?

Pneumonia is an infection of the lung. In most cases, the spread of infection from one person to another is by means of droplet infection or through respiratory route. In certain viruses it is seen that they can spread by contact.[14]

Q. How long does pneumonia remain contagious?

Bacteria or viruses generally have an infectious period. The infections caused by them spread maximum during that phase. The infectious period varies from organism to organism. In general we can remember it is a few days prior to starting of the infection, to few days after the disappearance of the infection. But the use of antibiotics and antivirals has brought down the number of days it can spread from an infected person.

Q. How is pneumonia treated?

General measures that can be given in any pneumonias include [22, 23]

  • Rest
  • Plenty of fluid intake
  • O2 supplementation if the patient is in distress
  • Analgesics/ Pain Killers if required

If it is a bacterial or viral pneumonia, Oral or intravenous antibiotics would be required according to the severity of the condition. In case of viral pneumonias, antibiotics may help in ruling out complicating bacterial infections [24]. Anti-fungal and anti-parasitic medications are used as necessary.

Q. What are the complications due to pneumonia?

  • Empyema – Pus collection in pleural space. [25]
  • Pleural effusion – Fluid collection in pleural space. [25]
  • Lung Abscess – Pus filled pockets in the lung tissue. [25]

Q. How can Pneumonia be prevented?

General Care such as avoid smoking [21], washing hands regularly and drinking plenty of water can help prevent pneumonia infection to an extent.

Vaccinations[26] – Such as those against organisms like Streptococcus pneumonia, hemophilus influenza, measles virus, varicella virus and pertussis virus, can help in preventing pneumonia by those organisms.


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Published on November 11th, 2017 by under Diseases and Conditions.
Article was last reviewed on January 12th, 2022.

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