Pneumonia: Immune System and Tiny Air Sacs

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Every year, more than 60,000 Americans die of pneumonia, an inflammation of the lungs that's usually caused by infection with bacteria, viruses, fungi or other organisms. Pneumonia is a particular concern for older adults and people with chronic illnesses or impaired immune systems, but it can also strike young, healthy people. Worldwide, it's a leading cause of death in children. There are many kinds of pneumonia ranging in seriousness from mild to life-threatening. Although signs and symptoms vary, many cases of pneumonia develop suddenly, with chest pain, fever, chills, cough and shortness of breath. Infection often follows a cold or the flu, but it can also be associated with other illnesses or occur on its own. Although antibiotics can treat some of the most common forms of bacterial pneumonias, antibiotic-resistant strains are a growing problem. For that reason, and because the disease can be very serious, it's best to try to prevent infection in the first place. Signs and symptoms

Pneumonia can be difficult to spot. It often mimics a cold or the flu, beginning with a cough and a fever. Chest pain is a common symptom of many types of pneumonia. Pneumonia symptoms can vary greatly, depending on underlying conditions and the type of organism causing the infection: Bacteria - Many types of bacteria can cause pneumonia. Bacterial pneumonia can occur independently, at the same time as viral pneumonia, or may develop after having a viral upper respiratory infection such as influenza. Signs and symptoms include: shaking chills, a high fever, sweating, shortness of breath, chest pain, and a cough that produces thick, greenish or yellow phlegm. Bacterial pneumonia is often confined to just one area (lobe) of the lung. This is called lobar pneumonia. Viruses - About half the reported cases of pneumonia are caused by viruses. Viral pneumonia tends to begin with flu-like signs and symptoms. It usually starts with a dry cough, headache, fever, muscle pain and fatigue. As the disease progresses, patients may become breathless and develop a cough that produces just small quantities of phlegm that may be clear or white. Patients with viral pneumonia run the risk of also developing a secondary bacterial pneumonia Mycoplasma - This tiny organism causes signs and symptoms similar to those of other bacterial and viral infections, although symptoms appear more gradually and are often mild and flu-like. Patients are usually not sick enough to stay in bed or to seek medical care and may never even know they've had pneumonia. That's why this type of pneumonia is often called walking pneumonia. Mycoplasma pneumonia spreads easily in situations where people congregate and is common among schoolchildren and young adults. Fungi - Certain types of fungus can cause pneumonia, although these types of pneumonia are much less common. Most people experience few if any symptoms after inhaling these fungi, but some develop symptoms of acute pneumonia, and still others may develop a chronic pneumonia that persists for months. Pneumocystis carinii - Pneumonia caused by P. carinii is an opportunistic infection that affects people living with AIDS. People whose immune systems are compromised by organ transplants, chemotherapy, or treatment with corticosteroids or other immune-suppressing drugs such as tumor necrosis factor (TNF) inhibitors also are at risk. The signs and symptoms of Pneumocystis carinii pneumonia include a cough that doesn't go away, fever, and shortness of breath. Causes

The lungs are two spongy organs surrounded by a moist membrane (the pleura). Each lung is divided into lobes, three on the right and two on the left. During inhalation, air is carried through the trachea to the lungs. The lungs contain major airways called bronchi. The bronchi repeatedly subdivide into many smaller airways (bronchioles), which finally end in clusters of tiny air sacs called alveoli. The body has mechanisms to protect the lungs from...
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