Overview

Respiratory tract infection (RTI) is a broad term for infectious illnesses that affect the airways and lungs. The term covers many conditions with varied severity, from self-limiting colds to life‑threatening pneumonias. Medical descriptions often distinguish infections by the anatomical region involved and by the responsible organisms — viruses, bacteria, fungi or, less commonly, parasites. For a general anatomical reference see the respiratory tract.

Anatomy and classification

Clinically RTIs are grouped into upper respiratory tract infections (URIs or URTIs) and lower respiratory tract infections (LRIs or LRTIs). URIs involve the nose, sinuses, pharynx and larynx and include common cold syndromes such as the common cold. LRIs affect the trachea, bronchi, bronchioles and lungs; this area includes the bronchioles and the lungs. Lower tract disease tends to be more serious: examples include bronchitis and pneumonia.

Causes and transmission

Viral pathogens are the most frequent cause of URIs, while both viruses and bacteria commonly cause LRIs. Typical viral agents include rhinoviruses, influenza viruses and respiratory syncytial virus; bacterial causes can include Streptococcus and Mycoplasma species among others. Transmission commonly occurs via respiratory droplets, direct contact with contaminated surfaces, or inhalation of aerosolized particles in poorly ventilated spaces.

Symptoms and diagnosis

Symptoms range with location and severity. Upper infections usually produce sore throat, nasal congestion, sneezing and cough. Lower infections often present with productive cough, shortness of breath, chest discomfort, fever and abnormal lung sounds on examination. Diagnosis combines clinical assessment, chest imaging when lower tract involvement is suspected, and laboratory testing such as rapid antigen tests, cultures or molecular assays to identify specific pathogens.

Treatment and prevention

Treatment depends on cause and severity. Viral infections are managed with supportive care: fluids, rest, fever control and, in some cases, antivirals for specific viruses. Bacterial infections may require antibiotics when indicated. Hospital care is needed for severe LRIs that compromise breathing. Preventive measures include vaccination where available (for influenza, pneumococcus and other targeted pathogens), hand hygiene, respiratory etiquette, appropriate ventilation and avoidance of close contact during outbreaks.

Public health importance and notable facts

Lower respiratory infections are a major contributor to illness and death globally, particularly among young children, older adults and people with chronic illnesses. Seasonal patterns and the emergence of novel respiratory pathogens make surveillance and vaccination key components of public health strategy. For more detailed anatomy and clinical guidance consult resources on the respiratory tract and condition-specific pages such as pneumonia and bronchitis. For general patient information about common mild infections see material on the common cold and on the structure of the lungs and bronchioles.

  • Common pathogens: viruses (rhinovirus, influenza), bacteria (Streptococcus, Mycoplasma).
  • Key prevention: vaccination, hand hygiene, masks in high‑risk settings.
  • When to seek care: difficulty breathing, high fever, persistent chest pain, or worsening symptoms.