The most common cause of pneumonia in adults > 30 years, in the absence of an ongoing viral pandemic such as COVID-19, is
Bacterial infection
Streptococcus pneumoniae is still the most common pathogen in all age groups, settings, and geographic regions. However, the incidence of S. pneumoniae infection has been declining because of increasing rates of vaccination and the development of herd immunity. However, pathogens of every sort, from viruses to parasites, can cause pneumonia. With the availability of sensitive molecular diagnostic methods, there is increasing recognition of viruses as a cause of pneumonia, either as a sole pathogen or as a co-pathogen with bacteria.
Categories of Pneumonia:
- Community-acquired
- Hospital-acquired (excluding ventilator-associated)
- Ventilator-associated
- Occurring in immunocompromised patients, including patients with human immunodeficiency virus (HIV) infection
- Aspiration pneumonia, which occurs when large volumes of the upper airway or gastric secretions enter the lungs
