What causes pneumonia?

Pneumonia is a lung infection caused by viruses or bacteria (germs). It can be found either by a doctor listening to the chest or by an X-ray. Pneumonia is not easily passed from one person to another.

Viruses, bacteria or (in rare cases) parasites or other organisms can cause pneumonia.

• In most cases, the specific organism (such as bacteria or virus) cannot be identified even with testing. When an organism is identified, it is usually the bacteria Streptococcus pneumoniae.
• Many types of bacteria may cause pneumonia. Pneumonia caused by Mycoplasma pneumoniae is sometimes mild and called "walking pneumonia."
• Viruses, such as influenza A (the flu virus) and respiratory syncytial virus (RSV) can cause pneumonia.

In people with impaired immune systems, pneumonia may be caused by other organisms, including some forms of fungi, such as Pneumocystis jiroveci (formally called Pneumocystis carinii). This fungus frequently causes pneumonia in people who have AIDS. Some doctors may suggest an HIV test if they think that Pneumocystis jiroveci is causing the pneumonia.

How do you get pneumonia? - You may get pneumonia:

• After you breathe infected air particles into your lungs.
• After you breathe certain bacteria from your nose and throat into your lungs. This generally occurs during sleep.
• During or after a viral upper respiratory infection, such as a cold or influenza (flu).
• As a complication of a viral illness, such as measles or chickenpox.
• If you breathe large amounts of food, gastric juices from the stomach or vomit into the lungs (aspiration pneumonia). This can happen when you have had a medical condition that affects your ability to swallow, such as a seizure or a stroke.

A healthy person's nose and throat often contain bacteria or viruses that cause pneumonia. Pneumonia can develop when these organisms spread to your lungs while your lungs are more likely to be infected. Examples of times when this can happen are during or soon after a cold or if you have a long-term (chronic) illness, such as chronic obstructive pulmonary disease (COPD).

You can get pneumonia in your daily life, such as at school or work (community-associated pneumonia) or when you are in a hospital or nursing home (healthcare-associated pneumonia). Treatment may differ in healthcare-associated pneumonia, because bacteria causing the infection in hospitals may be different from those causing it in the community.

Pneumonia is inflammation of lung tissue. You all realize organisms (bacteria, viruses, fungus and parasites) can get into our airways and inflame lung tissue causing cough trouble breathing less oxygen to rest of our body. Infection can enter through your blood or directly into our lungs. Also vomiting and 'aspirating' stomach contents (going 'down wrong pipe') can irritate and inflame our lungs. Children swallow objects that after being in lung will cause an inflammation. Inhaling irritants (including household cleaners) can cause our lung tissue to swell / inflame - pneumonia. Some of us are at increased risk for infections and specifically pneumonia. Chronic exposure to allergens toxins best example smoke can also inflame lung tissue allowing for your healthcare provider to hear abnormal sounds when using a stethoscope. You can have pneumonia days before a chest x-ray shows it! Be sure your provider listens to your lung fields - front and back in at least 8 areas and also asks you to say 'e' as he/she listens. You should have your mouth open and breath deep and not fast. When lung tissue is swollen (consolidated) 'e' will sound like 'a' thru the stethoscope. Remember if you are sent for an X-ray (plain film) to really take a deep breath otherwise you have been radiated for nothing. (Radiation dose from a chest film is 0.1 mSv or comparable to natural background radiation equal to 10 days of exposure.) A well preformed image must show at least 9 of your ribs to correctly evaluate the lung tissue underneath. If you have a 'documented' (on X-ray) pneumonia you should have a 'follow-up film to see how it resolved (yes you can hear the pneumonia is gone before the X-rays shows it is). Scar, calcification or other might remain - and you need to know this for the future.