what can you say about pneumonia?

Answer 1

Pneumonia is an illness of the lungs and respiratory system in which the alveoli (microscopic air-filled sacs of the lung responsible for absorbing oxygen from the atmosphere) become inflamed and flooded with fluid. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites. Pneumonia may also occur from chemical or physical injury to the lungs, or indirectly due to another medical illness, such as lung cancer or alcohol abuse.

Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing. Diagnostic tools include x-rays and examination of the sputum. Treatment depends on the cause of pneumonia; bacterial pneumonia is treated with antibiotics.

Pneumonia is a common illness which occurs in all age groups, and is a leading cause of death among the elderly and people who are chronically ill. Vaccines to prevent certain types of pneumonia are available. The prognosis for an individual depends on the type of pneumonia, the appropriate treatment, any complications, and the person's underlying health.



Symptoms

Pneumonia fills the lung's alveoli with fluid, keeping oxygen from reaching the bloodstream. The alveolus on the left is normal, while the alveolus on the right is full of fluid from pneumonia.People with infectious pneumonia often have a cough that produces greenish or yellow sputum and a high fever that may be accompanied by shaking chills. Shortness of breath is also common, as is pleuritic chest pain, a sharp or stabbing pain, either felt or worse during deep breaths or coughs. People with pneumonia may cough up blood, experience headaches, or develop sweaty and clammy skin. Other symptoms may include loss of appetite, fatigue, blueness of the skin, nausea, vomiting, mood swings, and joint pains or muscle aches. Less common forms of pneumonia can cause a variety of other symptoms. For instance, pneumonia caused by Legionella may cause abdominal pain and diarrhea, while pneumonia caused by tuberculosis or Pneumocystis may cause only weight loss and night sweats. In elderly people the manifestations of pneumonia may not be typical. Instead, they may develop new or worsening confusion or may experience unsteadiness leading to falls. Infants with pneumonia may have many of the symptoms above, but in many cases, they are simply sleepy or have decreased appetite.


[edit] Diagnosis
To diagnose pneumonia, health care providers rely on a patient's symptoms and findings from physical examination. Information from a chest X-ray, blood tests, and sputum cultures may also be helpful. The chest X-ray is typically used for diagnosis in hospitals and some clinics with X-ray facilities. However, in a community setting (general practice), pneumonia is usually diagnosed based on symptoms and physical examination alone. Diagnosing pneumonia can be difficult in some people, especially those who have other illnesses. Occasionally a chest CT scan or other tests may be needed to distinguish pneumonia from other illnesses.


[edit] Physical examination
Individuals with symptoms of pneumonia need medical evaluation. Physical examination by a health care provider may reveal fever or sometimes low body temperature, an increased respiratory rate, low blood pressure, a fast heart rate, or a low oxygen saturation, which is the amount of oxygen in the blood as indicated by either pulse oximetry or blood gas analysis. People who are struggling to breathe, confused, or who have cyanosis (blue-tinged skin) require immediate attention.



[edit] Viruses
Main article: viral pneumonia
Viruses must invade cells in order to reproduce. Typically, a virus reaches the lungs when airborne droplets are inhaled through the mouth and nose. Once in the lungs, the virus invades the cells lining the airways and alveoli. This invasion often leads to cell death, either when the virus directly kills the cells, or through a type of cell self-destruction called apoptosis. When the immune system responds to the viral infection, even more lung damage occurs. White blood cells, mainly lymphocytes, activate a variety of chemical cytokines which allow fluid to leak into the alveoli. This combination of cell destruction and fluid-filled alveoli interrupts the normal transportation of oxygen into the bloodstream.

In addition to damaging the lungs, many viruses affect other organs and thus can disrupt many different body functions. Viruses also can make the body more susceptible to bacterial infections; for this reason, bacterial pneumonia often complicates viral pneumonia.

Viral pneumonia is commonly caused by viruses such as influenza virus, respiratory syncytial virus (RSV), adenovirus, and metapneumovirus. Herpes simplex virus is a rare cause of pneumonia except in newborns. People with immune system problems are also at risk for pneumonia caused by cytomegalovirus (CMV).


[edit] Bacteria
Main article: bacterial pneumonia
Bacteria typically enter the lung when airborne droplets are inhaled, but they can also reach the lung through the bloodstream when there is an infection in another part of the body. Many bacteria live in parts of the upper respiratory tract, such as the nose, mouth and sinuses, and can easily be inhaled into the alveoli. Once inside the alveoli, bacteria may invade the spaces between cells and between alveoli through connecting pores. This invasion triggers the immune system to send neutrophils, which are a type of defensive white blood cell, to the lungs. The neutrophils engulf and kill the offending organisms, and they also release cytokines, causing a general activation of the immune system. This leads to the fever, chills, and fatigue common in bacterial and fungal pneumonia. The neutrophils, bacteria, and fluid from surrounding blood vessels fill the alveoli and interrupt normal oxygen transportation.


The bacterium Streptococcus pneumoniae, a common cause of pneumonia, photographed through an electron microscope.Bacteria often travel from an infected lung into the bloodstream, causing serious or even fatal illness such as septic shock, with low blood pressure and damage to multiple parts of the body including the brain, kidneys, and heart. Bacteria can also travel to the area between the lungs and the chest wall (the pleural cavity) causing a complication called an empyema.

The most common causes of bacterial pneumonia are Streptococcus pneumoniae, Gram-negative bacteria and "atypical" bacteria. The terms "Gram-positive" and "Gram-negative" refer to the bacteria's color (purple or red, respectively) when stained using a process called the Gram stain. The term "atypical" is used because atypical bacteria commonly affect healthier people, cause generally less severe pneumonia, and respond to different antibiotics than other bacteria.

The types of Gram-positive bacteria that cause pneumonia can be found in the nose or mouth of many healthy people. Streptococcus pneumoniae, often called "pneumococcus", is the most common bacterial cause of pneumonia in all age groups except newborn infants. Another important Gram-positive cause of pneumonia is Staphylococcus aureus. Gram-negative bacteria cause pneumonia less frequently than gram-positive bacteria. Some of the gram-negative bacteria that cause pneumonia include Haemophilus influenzae, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Moraxella catarrhalis. These bacteria often live in the stomach or intestines and may enter the lungs if vomit is inhaled. "Atypical" bacteria which cause pneumonia include Chlamydophila pneumoniae, Mycoplasma pneumoniae, and Legionella pneumophila.


[edit] Fungi
Main article: fungal pneumonia
Fungal pneumonia is uncommon, but it may occur in individuals with immune system problems due to AIDS, immunosuppresive drugs, or other medical problems. The pathophysiology of pneumonia caused by fungi is similar to that of bacterial pneumonia. Fungal pneumonia is most often caused by Histoplasma capsulatum, Cryptococcus neoformans, Pneumocystis jiroveci, and Coccidioides immitis. Histoplasmosis is most common in the Mississippi River basin, and coccidioidomycosis is most common in the southwestern United States.


[edit] Parasites
Main article: parasitic pneumonia
A variety of parasites can affect the lungs. These parasites typically enter the body through the skin or by being swallowed. Once inside the body, they travel to the lungs, usually through the blood. There, as in other types of pneumonia, a combination of cellular destruction and immune response causes disruption of oxygen transportation. One type of white blood cell, the eosinophil, responds vigorously to parasite infection. Eosinophils in the lungs can lead to eosinophilic pneumonia, thus complicating the underlying parasitic pneumonia. The most common parasites causing pneumonia are

Answer 2

Pneumonia is acute inflammation of the lungs caused by infection. Initial diagnosis is usually based on chest x-ray. Causes, symptoms, treatment, preventive measures, and prognosis differ depending on whether the infection is bacterial, viral, fungal, or parasitic; whether it is acquired in the community, hospital, or nursing home; and whether it develops in a patient who is immunocompetent or immunocompromised.
Please see the web pages for more details on Pneumonia, cytomegalovirus (CMV) pneumonia, Viral pneumonia and Pneumonia in immunocompromised host