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History:
Pneumonia has been a common disease throughout human history. The symptoms were described by Hippocrates (c. 460 BC – 370 BC).
Bacteria were first seen in the airways of individuals who died from pneumonia Edwin Klebs in 1875.
Initial work identifying the two common bacterial causes Streptococcus pneumoniae and Klebsiella pneumoniae was performed by Carl Friedlander and Albert Frankelin 1882 and 1884, respectively.
Although pneumonia was regarded by William Osier in the 19th century as “the captain of the men of death”, the advent of antibiotic therapy and vaccines in the 20th century has seen radical improvements in survival outcomes. Nevertheless, in the third world, and among the very old, the very young and the chronically ill, pneumonia remains a leading cause of death
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs (alveoli)—associated with fever, chest symptoms, and a lack of air space .Pneumonia is typically caused by an infection but there are a number of other causes. Infectious agents include bacteria, viruses, fungi, and parasites.
Classification of pneumonia:
Pneumonitis refers to lung inflammation; pneumonia refers to pneumonitis, usually due to infection. Pneumonia is most commonly classified by where or how it was acquired (community-acquired, aspiration, healthcare-associated, hospital-acquired, and ventilator- associated pneumonia), but may also be classified by the area of lung affected (lobar pneumonia, bronchial pneumonia and acute interstitial pneumonia), or by the causative organism. Pneumonia in children may additionally be classified based on signs and symptoms as non-severe, severe, or very severe.
Some causes of pneumonia are associated with classic, but non-specific, clinical characteristics. Pneumonia caused by Legionella may occur with abdominal pain, diarrhea, or confusion, while pneumonia caused by Streptococcus pneumoniae is associated with rusty colored sputum, and pneumonia caused by Klebsiella may have bloody sputum often described as “currant jelly”.
Signs and Symptoms:
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People with infectious pneumonia often have a productive cough, fever, accompanied by shaking chills, shortness of breath, sharp or stabbing chest pain during deep breaths, and an increased respiratory rate. More severe signs and symptoms may include decreased thirst, convulsions, persistent vomiting, or a decreased level of consciousness.
Cause:
Pneumonia is primarily due to infections of virus and bacteria. Mixed infections with both viruses and bacteria may occur in up to 45% of infections in children and 15% of infections in adults.
Bacteria (Bacterial pneumonia):
Bacteria are the most common cause of community acquired pneumonia, with Streptococcus pneumoniae isolated in nearly 50% of cases. Other commonly isolated bacteria include Haemophilus influenzae in 20%, Chlamydophila pneumoniae in 13%, Mycoplasma pneumoniae in 3%, Staphylococcus aureus, Moraxella catarrhalis, Legionella pneumophila and gram-negative bacilli.
Risk factors for infection depend on the organism involved. Alcoholism is associated with Streptococcus pneumoniae, anaerobic organisms, and Mycobacterium tuberculosis, smoking is associated with Streptococcus pneumonia, Haemophilus influenza etc.
Viruses (Viral pneumonia):
In adults, viruses account for approximately a third of pneumonia cases. Commonly implicated agents include: rhinoviruses, coronaviruses, influenza virus, respiratory syncytial virus (RSV), adenovirus, and Para influenza.
Fungi (Fungal pneumonia):
Fungal pneumonia is uncommon, but it may occur in individuals with weakened immune systems due to AIDS, immunosuppressive drugs, or other medical problems.
Parasites (Parasitic pneumonia):
A variety of parasites can affect the lungs. The most common parasites causing pneumonia are Toxoplasma gondii, Strongyloides stercoralis and Ascariasis.
Idiopathic (Idiopathic interstitial pneumonia):
Idiopathic interstitial pneumonia or noninfectious pneumonia are a class of diffuse lung diseases
Pathophysiology:
Pneumonia fills the lung’s alveoli with tluid, hindering oxygenation. The alveolus on the left is normal, whereas the one on the right is full of tluid from pneumonia.
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Pneumonia frequently starts as an upper respiratory tract infection that moves into the lower respiratory tract.
Diagnosis:
Pneumonia is typically diagnosed based on a combination of physical signs and a chest X-ray. In adults, investigations are in general not needed in mild cases of pneumonia. But in severe cases, pulse oximetry, chest radiography, and blood tests including a complete blood count, serum electrolytes, C-reactive protein, and possibly liver function tests are recommended.
Microbiology:
For those not responsive to treatment, sputum culture should be considered, and culture for Mycobacterium tuberculosis should be carried out in those with a chronic productive cough.
Differential diagnosis:
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Several diseases can be similar to pneumonia, including: chronic obstructive pulmonary disease (COPD), asthma, pulmonary edema, bronchiectasis, lung cancer, and pulmonary emboli.
Prevention:
Prevention includes vaccination, environmental measures, and appropriately treating the disease.
Vaccination:
Vaccination is effective for preventing certain bacterial and viral pneumonias in both children and adults.
Influenza vaccines are modestly effective against influenza A and B. The Center for Disease Control and Prevention (CDC) recommends for yearly vaccination. When an influenza outbreak is occurring, medications such as amantadine, rimantadine, zanamivir, and oseltamivir can help prevent influenza. A vaccine against Streptococcus pneumoniae is also available for adults.
Environmental:
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Reducing indoor air pollution is recommended along with no smoking.
Other:
Appropriately treating underlying illnesses (such as AIDS) can decrease a person’s risk of pneumonia
Management:
Typically, oral antibiotics, rest, simple analgesics, and fluids suffice for complete resolution.
Bacterial:
Antibiotics like cephalosporins, carbapenems, fluoroquinolones, aminoglycosides, and vancomycinmay be recommended. These antibiotics, are often given intravenously, may be used in combination.
Viral:
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Neuraminidase inhibitors may be used to treat viral pneumonia caused by influenza viruses (influenza A and influenza B). No specific antiviral medications are recommended for other types of community acquired viral pneumonias including coronavirus, adenovirus, Hantavirus and Para influenza virus.
Aspiration:
In general, aspiration pneumonitis is treated conservatively with antibiotics indicated only for aspiration pneumonia which include clindamycin, a combination of a beta-lactam antibiotic and metronidazole, or an aminoglycoside
Pleural effusion, empyema, and abscess:
In pneumonia, a collect ion of fluid (pleura) effusion) often forms in the space, that surrounds the lung (the pleural cavity). Occasionally, microorganisms will infect this fluid, causing what is called an empyema which can be distinguished from Para pneumonic effusion by examination.
Epidemiology:
Pneumonia is a common illness affecting approximately 450 million people a year and occurring in all parts of the world.
