Community Acquired Pneumonia – Symptoms, Diagnostic Tests and Treatment

Community Acquired Pneumonia (CAP) is a common and potentially serious infection of the lungs. It can lead to hospitalization and death in the elderly or those who have significant, pre-existing illnesses.

Bacteria, viruses and fungus can all cause pneumonia. Viral and fungal causes of pneumonia are not typical. This is important because the antibiotic chosen for treatment depends on the causative agent. Since X-rays and typical out-patient lab work do not identify the causative agent, treatment is based on the most likely cause. Typically, CAP is caused by bacteria of which the most common is Streptococcus pneumoniae.

Who needs to be hospitalized?

For the most part, otherwise healthy individuals with no significant pre-existing illness can be treated for pneumonia as an outpatient.

Hospitalization depends on the following factors:

  • Age> 65 years
  • Presence of other chronic illnesses (heart, kidney or lung problems, poorly controlled diabetes are the main ones)
  • People on immunosuppressants (cancer or HIV patients)
  • Cognitive or physical disabilities
  • Severity of presenting symptoms (breathing rate, blood pressure, confusion etc)

What are the symptoms of CAP?

  • Fever> 100.4
  • Cough with or without sputum
  • Wheezing
  • Pleuritic chest pain (sharp, stabbing pain with breathing)
  • Heart rate> 100 beats / minute
  • Respiration rate> 20 breaths / minute
  • Fatigue
  • Body aches, chills, nausea, vomiting or diarrhea can also be associated with CAP


The more symptoms present, the more likely the diagnosis. However, you do not need to have every one of them to have pneumonia. I'm reminded of a patient I had years ago whose only symptoms were flank pain and fever. He was convinced he had kidney stones but the clinical exam and other tests did not match the picture.

So despite the importance of listening to the patient's symptoms, the diagnosis can not be made without a thorough clinical exam and when appropriate, diagnostic tests.


It may take several days for a pneumonia to show up on x-ray. That's why x-rays may not be ordered by your provider.

Blood work

Depending on the clinical exam, your age and any other chronic illnesses, your provider may decide to order blood work.

In the early stages of pneumonia, these tests may come back normal so that's why in an otherwise healthy adult, your provider may decide to treat you with antibiotics, rather than order these tests.


Certain classes of antibiotics are ordered depending on the likely causative agent, your age and whether you've been treated with an antibiotic within the last three months.

With the exception of azithromycin, treatment with traditional antibiotics lasts anywhere from 7-14 days depending on the type of antibiotic used. Azithromycin is generally a 5 day course but it continues to work in your system for about 10 days.


Over 70% of people with pneumonia continue to report fatigue one month after being treated. Although usual activities may resume a week or so after treatment finishes, do not expect to be back to your usual self. This does not mean that you still have pneumonia unless your symptoms continue to persist. In the vast majority of cases, it just means that it takes time to fully return to your baseline.

Remember – do not self diagnose. See your provider if you have any concerns.