The most common lower respiratory tract infection (LRI) is pneumonia. Pneumonia is an infection that inflames the air sacs in one or both lungs, causing them to fill with fluid or pus. It can be caused by various pathogens, including bacteria, viruses, and fungi.
The majority of pneumonia cases are caused by bacteria, with Streptococcus pneumoniae being the most common bacterial pathogen. Other bacteria that can cause pneumonia include Haemophilus influenzae, Mycoplasma pneumoniae, Legionella pneumophila, and Staphylococcus aureus, among others. Bacterial pneumonia often occurs as a complication of a respiratory tract infection or when the immune system is weakened.
Viral pneumonia is also common and is caused by several viruses, including influenza viruses (such as influenza A and influenza B), respiratory syncytial virus (RSV), adenoviruses, and coronaviruses. Viral pneumonia can be particularly severe in certain populations, such as young children, older adults, and individuals with weakened immune systems.
Other types of lower respiratory tract infections include bronchitis, bronchiolitis, and tuberculosis, but pneumonia remains the most prevalent and commonly encountered lower respiratory infection.
It’s important to note that the specific prevalence and distribution of different lower respiratory tract infections may vary across regions and populations. Additionally, the emergence of new pathogens or strains can influence the frequency and distribution of LRIs over time.