CAP

By Peter Galvin, MD

Community-acquired pneumonia (CAP) simply means pneumonia that is contracted outside of a hospital setting. Pneumonia is an infection of part of a lung that can be caused by various infectious agents. Once the infection is detected by the immune system, it sends antibodies and cells, for example T white cells, to fight the infection. As a result, debris from this infectious battle builds up in the air sacs, or alveoli, of the lung and can be seen on chest X-ray and found by physical examination. Placing a stethoscope over the infection site can detect crackles, or rales, that are heard with each breathe the patient takes, and asking the patient to say “E” will sound like “A.” Because the lungs are air-filled, tapping on, or percussing, a normal chest will sound hollow, like tapping on a drum. Percussing a lung with pneumonia will sound dull, like a thud.

CAP in the U.S. results in about 14 million ER visits, 740,000 hospitalizations, and over 40,000 deaths per year. Mortality is 2.8% for those younger than 60 years and 26.8% for those 80 and older. Risk factors include older age (>65 years), cigarette smoking, lung diseases like asthma and COPD, and chronic conditions like HIV, cancer diabetes, and heavy alcohol abuse. CAP can be caused by viruses, fungi, and bacteria. Among those hospitalized with CAP, viruses and the bacterium Streptococcus pneumoniae are the most common causes. Symptoms include fever, chills, cough with or without sputum (mucus in the lower airways), shortness of breath, chest pain, confusion, and fatigue. In most cases, an elevated white blood cell level is found.

If physical examination finds signs of pneumonia, chest X rays are indicated. If X rays are negative or equivocal, chest CT scan should be performed. All patients with CAP should be tested for influenza and Covid-19. Hospitalized patients with severe symptoms should also get sputum and blood cultures. Typically, outpatients can be treated with oral antibiotics, usually amoxicillin or doxycycline, for seven to 10 days. Hospitalized patients are usually treated with intravenous antibiotics, and those with severe symptoms may require intravenous steroids and, sometimes, ICU care and mechanical ventilation if they develop respiratory failure.

Prevention of CAP involves reducing risk by stopping smoking and reducing alcohol consumption plus receiving all relevant vaccinations including flu vaccine, and for some Covid-19 and RSV vaccines. Since Strep pneumoniae accounts for most bacterial CAP, those at highest risk, namely those aged 5-years and younger and 50-years and older should be vaccinated against strep. A vaccine for strep first became available in 1983 as Pneumovax 23. Typically, this vaccine required multiple doses. More recently, Prevnar 13, then Prevnar 20, which became available in 2021, are preferred because often, only one dose is required.

For more information go to the website of the Centers for Disease Control and Prevention at www.cdc.gov

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