Introduction
Pneumonia is a pulmonary disease caused by an infection in one or both lungs. Viruses, bacteria, or fungi cause the infection, which can present as mild, serious, or even life-threatening.
Each year, pneumonia infects about 450 million people worldwide and causes nearly 4 million deaths.
In the United States, it infects about a million Americans every year and causes approximately 50,000 deaths.
With the introduction of newer antibiotics and vaccines in the 20th century, survival has greatly improved.
12th November was declared in 2009 as the annual World Pneumonia Day, a day to raise awareness and take action against the disease by policymakers and more than 100 organizations.
Viral pneumonia is more common than bacterial pneumonia though bacterial pneumonia tends to be more severe and may likely require hospitalization.
Viral pneumonia accounts for between 13% and 50% of cases and bacterial pneumonia accounts for between 8% – 13%.
In some cases, both infections can co-exist, increasing the chance of severity and a more adverse outcome, which may require admission to ICU.
Fungal pneumonia is less common than bacterial and viral pneumonia and can be serious, if not treated.
Mixed viral and bacterial infections occur in about 45% of infections in children and 15% of infections in adults.
Pneumonia affects all ages, but infants, young children, people older than 65 years, smokers with chronic lung conditions, and those with weakened immune systems tend to have a serious outcome.
In pneumonia, the alveoli or air sacs of the lung parenchyma get inflamed due to the pneumonic infection causing them to be filled with pus or fluid.
Alveoli are tiny sacs present in clusters at the end of the branches of the airways (bronchioles).
Lobar pneumonia affects one or more lobes of the lungs. Bronchopneumonia infects patches throughout both the lungs.
Types of pneumonia – Classification
Pneumonia can be classified in several ways: by the place where you acquire it, by the type of organism that causes it, and by the area of the lung that it affects.
Pneumonia is caused by several types of bacteria, viruses, fungi, or mycoplasma, which is a bacteria-like organism.
You can get pneumonia in three ways: from the community, from the hospital, and by breathing in food particles, vomit, etc
Community-acquired pneumonia (CAP)
Community-acquired pneumonia is pneumonia that you acquire from the general population or the community that you live in. This is the most common way in which you can get pneumonia.
It can be bacterial or viral and generally manifests as an acute infection, with symptoms appearing over the course of hours or days.
The Streptococcus pneumonia bacteria is the leading cause of bacterial community-acquired pneumonia.
Haemophilus influenza, Staphylococcus aureus, Legionella pneumophila, Mycoplasma pneumonia, are viruses that are the leading causes of viral community-acquired pneumonia.
Hospital-acquired pneumonia (HAP)
Hospital-acquired pneumonia (HAP) is pneumonia that you acquire in a hospital or in a healthcare facility like outpatient clinics and kidney dialysis centers.
Pneumonia acquired in this way is a serious lung infection that a patient acquires at least two days after being admitted to a hospital. It’s usually a bacterial pneumonia and not caused by a virus.
HAP can be very serious and sometimes fatal. This is because patients’ immune systems are already weakened by a prevalent illness, and the strain of infecting organism is resistant to the drugs that are usually used to treat pneumonia.
Aspiration pneumonia
Aspiration pneumonia is an infection that develops in the lungs caused by the inhalation (breathing in) of saliva, food, liquid, vomit, or even small foreign objects.
Aspiration pneumonia is caused by a bacterial infection and can be successfully treated with oxygen and antibiotics. If left untreated, serious complications can be even fatal.
It is not common in healthy individuals and occurs more in people having conditions that cause swallowing difficulty.
Symptoms
Pneumonia is not always serious. Symptoms can be so mild that you may not notice them, or they can be so serious that you may have to be hospitalized.
The severity of the infection depends on the virility of the organism causing the infection, your age, and your overall health status (meaning your body’s immunity).
Mild symptoms are often akin to those of flu, but in pneumonia, they last longer. Signs and symptoms of pneumonia may include some of the following:
- Cough with whitish or greenish, yellow, or bloody expectoration
- Fever with shaking chills accompanied by sweating
- Shortness of breath, which worsens on physical activity
- Rapid and shallow breathing
- Rapid heartbeat
- Sharp or stabbing chest pain that is aggravated by coughing or taking a deep breath. The chest pain is located on the side of the infected lung. Severe abdominal pain can occur when the pneumonia is located in the lower lobes of the lung.
- Loss of appetite and fatigue
- Nausea, vomiting, or diarrhea especially in small children
- Confusion, especially in older people above the age of 65 years
More severe signs and symptoms in children may include:
- blue-tinged skin
- refusing to drink
- convulsions
- continuing vomiting
- extreme temperatures
- decreased level of consciousness
How symptoms can vary according to the infecting agent?
Bacterial pneumonia symptoms
Bacterial pneumonia symptoms tend to be more severe and invariably require medical intervention. They can develop gradually or suddenly. They can include:
- Fever that may climb as high as 105 degrees F and is accompanied by profuse sweating.
- There is a faster breathing and heart rate
- Lips and nail beds acquire a bluish tinge due to low oxygen levels in the blood (cyanosis).
- The patient appears confused or delirious.
Viral pneumonia symptoms
The symptoms of viral pneumonia usually develop gradually over several days.
Early symptoms include:
- Fever
- A dry cough
- Headache
- Muscle aches
- Weakness
The symptoms typically soon worsen and include:
- Increasing cough
- Difficulty breathing
- High fever
- Blueness of the lips (cyanosis)
Fungal pneumonia symptoms
Since most symptoms of fungal, bacterial, and viral pneumonia are similar, diagnosing the causative organism and arriving at a more focused treatment can be delayed.
Presenting symptoms of fungal pneumonia are:
- Fever with chills
- Cough with thick, colored phlegm
- Shortness of breath
- Pain in the chest on deep breaths or coughing
- Nausea, vomiting, and diarrhea
- In older adults, the condition can also lead to mental confusion, which should be immediately addressed by the attending physician.
- In infants and toddlers, fungal pneumonia can cause difficulty feeding, pale skin, breathing difficulties, less urine production, and irritability.
Complications
Pneumonia usually responds well to treatment, but at times, this may not happen. At such times, pneumonia can be very serious and even deadly.
Complications mostly develop especially in people belonging to the high-risk group, which includes elderly people, very young children, those with a weakened immune system, among others.
Complications of pneumonia can include:
Sepsis.
In sepsis, the infection from the lungs gets into the blood (bacteremia) resulting in an overwhelming response of the immune system. Without prompt treatment, the infection can spread to the organs and can lead to multiple organ failure, tissue damage and death.
Bacteremia
Bacteremia due to pneumonia can cause loss of limbs. This happens because toxins produced by the infecting bacteria in the blood cause damage to the capillaries, which interferes with the blood supply to the limbs and causes death of tissue. When there is loss of too much tissue, the affected limb may need amputation. Besides, pneumococcal bacteremia can be fatal. It kills about 1 in 30 affected children and about 1 in 8 affected adults.
Difficulty breathing
In a severe case of pneumonia with an underlying chronic lung disease, you may have difficulty breathing, which can cause low blood oxygen levels. This may require hospitalization and the use of a ventilator till your pulmonary infection resolves.
Respiratory failure
In pneumonia, there is infection of the alveoli (air sacs) causing pus and fluid to accumulate in the air sacs. This makes it harder for the gaseous exchange to take place in the air sacs because of which the lungs cannot provide enough oxygen in the blood leading to a build-up of carbon dioxide in the blood. This requires the use of a ventilator to restore oxygen levels. COPD patients who have developed pneumonia are especially vulnerable to this complication because the lungs are already damaged and pneumonia makes this condition worse.
Parapneumonic pleural effusion (Hydrothorax)
In bacterial pneumonia, the infection in the lungs and airways can spread to the pleura, which are membranes covering the lungs. This can cause fluid to build up in the pleural cavity. This is called pleural effusion.
Empyema
Empyema is defined as a collection of purulent fluid (pus) in the pleural cavity. Pneumonic infection in the lungs spreads into the pleural space and causes infection and the formation of pus in the pleural cavity. When this fluid gets infected, it has to be drained out by a chest drainage tube or has to be surgically removed.
Lung abscesses
Pockets of pus can form at the sites of infection in the lung parenchyma. They are treated with oral and parenteral antibiotics and additionally, may be required to be drained out with a long needle or a drainage tube. At times, this may require surgery.
Pneumothorax
Lung abscesses near the pleura of the lungs can cause perforation of the pleural membranes and cause air to collect within the pleural cavity. There are two fallouts to this type of development. The collection of air in the pleural cavity is called pneumothorax, which can cause part or full collapse of the lung. This is called Atelectasis.
Worsening of underlying health problems
In people with pre-existing cardiovascular conditions, pneumonia can worsen these conditions, which can lead to dangerous complications such as a heart attack or worsening heart failure.
Meningitis
Pneumococcal meningitis is caused by Streptococcus pneumoniae bacteria (also called pneumococcus, or S pneumoniae), which is the same bacterial strain that causes pneumococcal pneumonia. Pneumococcal meningitis can occur when the Streptococcus pneumonia bacteria invade the bloodstream, cross the blood-brain barrier, and proliferate in the fluid present between the meninges (membranes covering the brain). About 1 in 12 children and 1 in 6 older adults who get pneumococcal meningitis succumb to the infection.
Long-term complications
Children who recover from pneumonia have an increased risk of chronic lung diseases in the future. The long-term effects associated with early childhood pneumonia include obstructive lung function deficits, an increased risk of asthma in adulthood, COPD, and bronchiectasis.