Pneumonia is an infection or inflammation of the lungs. It can be in just one part of the lungs, or it can involve many parts. Pneumonia is caused by bacteria, viruses, fungi, and other microorganisms. The severity of pneumonia depends on which organism is causing the infection. Viral pneumonias are usually not very serious, but they can be life-threatening in very old and very young patients, and in people whose immune systems are weak.
Even severe acute respiratory syndrome (SARS), which is believed to have a viral cause, has caused very few deaths.
Viral pneumonia can be caused by the influenza virus, respiratory syncytial virus (RSV), and the herpes or varicella viruses, including those that cause the common cold (parainfluenza and adenoviruses).
Influenza A and B usually occur in the winter and spring. In addition to the respiratory symptoms, you can get a headache, fever, and muscle aches. Your chance of catching the flu falls a lot (but is not totally prevented) if you get a "flu shot" every year.
Respiratory syncytial virus (RSV) is most common in the spring. It usually infects children and can cause outbreaks in daycare centers.
Herpes or varicella pneumonia are rare unless you are infected with chickenpox.
Symptoms of pneumonia caused by a virus usually go on for several days to a few weeks before you call your doctor. Most people with bacterial pneumonia get sick very quickly and see a doctor within a few days.
When to Seek Medical Care
Go to your hospital's emergency department or call your doctor if you develop any of these symptoms:
Shortness of breath, either at rest or with just a little exertion
Severe chest pain
Coughing up blood
Vomiting so much that you are dehydrated
Exams and Tests for Pneumonia
To see if you have pneumonia, your doctor will check your temperature, heart rate, and blood pressure. A small clamp, which looks like a clothespin, can be put on your finger to check your blood oxygen level. Your doctor will listen to your heart and lungs to help determine the cause of your symptoms and the severity of your illness. If it is possible that you have pneumonia, you will probably have a chest X-ray. Blood tests are not very helpful in diagnosing pneumonia except in special circumstances.
Influenza A and B are usually diagnosed through its symptoms -- fever, headache, body aches, tiredness, cough, runny nose. No lab tests are needed. Sometimes, secretions from your nose can be tested to help identify the organism.
Varicella pneumonia usually occurs during an outbreak of the chickenpox which makes it fairly easy to diagnose.
If your doctor suspects respiratory syncytial virus (RSV), a swab of your nose secretions can be sent for testing by a lab. Children and infants are more likely to be tested for RSV, because this virus can be more serious for them.
Adenovirus and parainfluenza virus are not likely to cause life-threatening illness. Tests are rarely done if these viruses are suspected to be the cause of pneumonia.