Pneumonia is an infection of the lungs caused by a variety of germs. These germs reach the air sacs (lowest part of airways) after inhalation, overcoming body’s normal defense mechanism like nasal hairs, mucus and cough which are weakened by smoking or dust inhalation. Once in the lungs, these microorganisms cause inflammation and filling of the air sacs with pus which makes it difficult for oxygen to reach the blood. A healthy person often recovers quickly with regular care. But it can be serious in people with a weak immune system. Infants, young children and elders are specially vulnerable to the infection.

Pneumonia is transmitted from person to person by airborne droplets. The sick person expels bacteria during sneezing, coughing or talking. People living in close proximity or in crowded settings like schools or hostels can inhale the organism. It may take from few days up to few weeks for the person to develop pneumonia after inhalation of the organism depending on the type of organism, amount inhaled and immune status of the person.

Symptoms:

The symptoms of pneumonia can be mild or could be life threatening depending on type and amount of microorganism and age and general health of the person.  Signs and symptoms of pneumonia include:

• Fever, which may occur with chills and rigor.
• Cough that  may produce yellow or bloody sputum.
• Difficulty breathing with rapid fast breathing.
• Chest pain which is sharp on deep inspiration.
• Some may also have nausea, vomiting or diarrhea.
• Altered mental status in elderly.
• People at extremes of age and weak immune system may not develop fever and instead may become hypothermic.

As severity of pneumonia increases, the patient may become lethargic. The patient may turn blue and show signs of labored breathing, which are danger signs.

Causes

Most forms of pneumonia are caused by the bacteria and viruses present in the air we breath.

Bacteria:

• Streptococcus pneumoniae – the most common cause of pneumonia.
• Mycoplasma pneumoniae – causes “walking pneumonia”.
• Staphylococcus aureus.
• Klebsiella pneumoniae.
• Tuberculosis.
• Pseudomonas aeruginosa.

Viruses:

• Influenza.
• Respiratory syncytial virus-more common in children less than 5 years.

Fungi:

• Fungi found in soil and bird droppings ( Histoplasmosis, Aspergillosis). This is relatively uncommon, seen mainly in people with chronic illness and weak immune system.

Pneumonia can be classified into three types based on where you got the infection. If a person was at home or in the community, it is called community acquired pneumonia (CAP). Patient may develop pneumonia during hospital stays for other chronic illness. This form of infection is called hospital acquired pneumonia (HAP). A person on a ventilator for a long duration may also develop pneumonia, which called ventilator associated pneumonia (VAP). The common organisms that cause pneumonia in these different setting are slightly different and so are the treatment options and the prognosis.

Risk factors

People with the following conditions are at risk of pneumonia:

• Smokers: the defense mechanisms of lungs (cough, mucus clearance, etc.) are decreased due to smoking.
• Older age people.
• Structural lung diseases like Chronic obstructive pulmonary disease (COPD), bronchiectasis  increase the chances of pneumonia.
• Alcoholics: aspiration of material into airways causes infection of lungs.
• Viral infections like influenza.
• Weak immune system: HIV, malnutrition (especially in children), medicines that suppress immune system ( like steroids, anti cancer drugs).
• Exposure to bird droppings (Chlamydia pneumoniae), poultry (bird flu) or farm animals (Q fever) increases the risk of certain types of pneumonia.
• Infants and young children are likely develop respiratory insufficiency because of pneumonia.

When to seek medical care

Early treatment of pneumonia can save lives, especially of infants and small children. So it is wise to seek care when fever and fast breathing is seen. The following signs warrant an urgent need to seek medical care:

• Bluish discoloration of lips or fingers suggests critically low oxygen exchange by the lungs.
• Poor feeding in infants; inability to suck.
• Distressed breathing: noisy breathing with movement of neck muscles on respiration.
• Inability to speak full sentences due to breathlessness.
• Chest indrawing, especially in children.
• Lethargy or unconsciousness is present in advanced disease and may obscure other danger signs like difficulty breathing.

Treatment options

In addition to history and physical exam, chest x-ray, blood and sputum tests are done to make the diagnosis for pneumonia. Additional tests may be needed based on clinical situation. Pneumonia is treated by antibiotics and proper supportive measures. Severe pneumonia needs hospitalization. Mild cases can be treated at home.

Antibiotics such as Amoxicillin, azithromycin, or cephalosporin are commonly used to treat bacterial pneumonia. Paracetamol or Acetaminophen can be given for fever. Nebulized saline helps to clear secretions and make breathing easier.

If not properly treated on time, pneumonia can be complicated by accumulation of  fluid/pus around the lungs. It can also spread the bacteria through blood to bone (osteomyelitis), brain (meningitis), or other tissues of the body. But respiratory failure is the most serious complication of pneumonia.

Prevention

Vaccination against Influenza and pneumonia help prevent this disease or its complication. Pneumococcal vaccine has been introduced to immunization schedule for infants in many developing countries fairly recently. Stopping smoking and alcohol use improves airway defense mechanisms and helps prevent pneumonia.