Pneumonia is a pathological infection of one or both lungs. It is characterized by the inflammation of lungs. It is mainly caused by bacteria, fungi, viruses or parasites. It generally starts following an infection in the upper respiratory tract. After this infection, symptoms appear after 2-3 days of cold or sore throat. People older than 65 years or younger than 2 years of age and those with impaired immune system or chronic illnesses are at a higher risk of pneumonia. There are more than 50 types of this infection that range in severity from mild to life-threatening. Pneumonia accounts for the death of more than 60,000 people in the United States every year. Symptoms In most cases, people have the symptoms of cold before developing pneumonia. It is followed by high fever, cough and chills. Severity of symptoms varies according to the causes and age of the patient. Chest pain is the most common symptom in most types.

• Bacterial pneumonia: This type leads to symptoms such as high fever, chills, chest pain, sweating, cough with thick, yellow or greenish sputum and shortness of breath.
• Viral pneumonia: This type is characterized by the signs that are similar to flu-like symptoms. It generally starts as a dry cough, fever, fatigue, headache and muscle pain. When the disease progresses, it causes shortness of breath and cough with small quantities of clear or white phlegm. It invites the risk of developing a secondary bacterial pneumonia.
• Fungal pneumonia: This type is not common. Some people may develop acute pneumonia after inhaling the fungi, while some may develop chronic pneumonia.
• Pneumonia due to Mycoplasma: Mycoplasma are a genus of bacteria in which cell walls are absent, causing a lot of antibiotics to be ineffective against them as most antibiotics usually interrupt cell wall synthesis to kill the organisms. Mycoplasma cause symptoms similar to those caused by bacterial and viral pneumonia. These symptoms may be flu-like and mild. You may not require any medical treatment for this type. That's why it is known as walking pneumonia.
• Pneumocystis carinii: It is an opportunistic organism that causes infection in people with AIDS. It can lead to pneumonia. The signs of such type are persistent cough, fever and shortness of breath.

Causes Pneumonia is mainly caused by infections from microorganisms such as bacteria, fungi and viruses. Bacterial infection is the most common and most serious. Streptococcus pneumoniae is the most common bacterial species causing this infection in adults. Mycoplasma pneumoniae is the common microorganism causing this infection in children of 2-3 years of age. There are different types of pneumonia depending upon the cause of disease such as:

• Community-acquired (acquired at work or school)
• Hospital-acquired (gastroesophageal reflux disease is the predisposing factor)
• Aspiration (because of inhaling foreign matter)
• Pneumonia caused by opportunistic organisms (common in people with compromised immune system)
• Emerging pathogens such as outbreaks of H5N1 influenza virus/bird flu and severe acute respiratory syndrome (SARS)

Is Pneumonia Really Contagious? This infection in itself is not contagious but bacteria and viruses that cause it can be contagious. People, when exposed to infection may catch the symptoms of normal cough and cold symptoms. It is not necessary that each person, exposed to cold virus or bacteria, develops pneumonia. It depends on the susceptibility and immunity of that individual. Transmission of infection may occur due to direct exposure to infectious secretions. Also, pneumonia pathogens can be transmitted from an ailing individual to healthy persons till about 3 days after starting off the antibiotic, antiviral or antifungal medication course (depending upon the class of pathogen). A good indication of whether or not pneumonia can still be contracted from someone is to look out for fever - if the patient does not have a fever or has ceased to have frequent chills and temperature fluctuations, he/she can be considered 'clean'. Diagnosis and Treatment Diagnosis is based on the physical examination, imaging tests such as X-ray, bronchoscopy and certain laboratory investigations such as sputum examination and blood tests such as white blood cell count. Treatment options depend upon the cause and can be treated with antibiotics, antiviral and antifungal medications, etc. Some over-the-counter medications are also recommended to treat pain, reduce fever and soothe coughing and sore throat.