Pneumonia is a respiratory infection that inflames the air sacs in one or both lungs, which may fill with fluid or pus. When this condition develops outside of a hospital or other healthcare facility, it is known as community-acquired pneumonia (CAP). Understanding how CAP spreads is important for protecting personal health and the well-being of those around you.
What is Community-Acquired Pneumonia?
Community-acquired pneumonia is an acute lung infection. It causes the oxygen-absorbing areas of the lung, known as alveoli, to become colonized by pathogenic microorganisms. The resulting inflammation and tissue damage can cause fluid to accumulate, hindering lung function and leading to symptoms such as fever, cough, and shortness of breath.
A wide range of microorganisms can cause CAP, with bacteria and viruses being the most frequent culprits. Common bacterial causes include Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella species. Viral agents frequently implicated in CAP cases include influenza virus, respiratory syncytial virus (RSV), rhinoviruses, and SARS-CoV-2. Less common causes involve fungi such as Histoplasma capsulatum, Coccidioides immitis, and Blastomyces dermatitidis.
How Community-Acquired Pneumonia Spreads
While pneumonia itself is not directly contagious, the bacteria and viruses that cause it can spread from person to person. The contagiousness of CAP depends largely on the specific pathogen responsible for the infection. These germs commonly spread through respiratory droplets released into the air when an infected person coughs, sneezes, or even talks. Individuals can also contract these germs by touching contaminated surfaces and then touching their own nose or mouth.
Bacterial causes of CAP are contagious. For bacterial pneumonia, an individual is contagious for about 24 to 48 hours after beginning antibiotic treatment and once their fever has subsided. However, the contagious period can extend if treatment is not administered or if the infection is severe. Viral causes of pneumonia, including influenza, can also be highly contagious, with the period of contagiousness lasting until symptoms, particularly fever, begin to improve.
Developing full-blown pneumonia after exposure to these pathogens depends on several factors, including the individual’s immune system and the amount of exposure. In contrast to bacterial and viral forms, pneumonia caused by fungi is not contagious from person to person.
Preventing the Spread of Community-Acquired Pneumonia
Preventing the spread of community-acquired pneumonia involves a combination of good hygiene practices and immunization. Frequent handwashing with soap and water reduces the transmission of germs. Covering coughs and sneezes with a tissue or elbow, rather than hands, helps contain respiratory droplets. Avoiding close contact with individuals who are sick also minimizes exposure to infectious agents.
Vaccinations play a significant role in preventing several common causes of CAP. Annual influenza shots are important because the flu virus can directly cause pneumonia or predispose individuals to secondary bacterial pneumonia. Pneumococcal vaccines protect against Streptococcus pneumoniae. These vaccines are recommended for adults over 65, and for younger individuals with certain underlying health conditions like chronic heart, lung, or kidney disease, diabetes, or a weakened immune system. Additionally, the COVID-19 vaccine can help prevent severe pneumonia caused by the SARS-CoV-2 virus.
Maintaining a healthy lifestyle supports the body’s defenses against infections. Adequate rest, a balanced diet, and regular physical activity contribute to a robust immune system. Quitting smoking is beneficial, as tobacco use damages the lungs’ ability to fight off infections, increasing the risk of pneumonia. Managing existing chronic health conditions, such as asthma or diabetes, also helps reduce susceptibility to CAP.