Droplet transmission refers to the spread of infectious agents via respiratory droplets expelled from the mouth or nose of an infected person during coughing, sneezing, talking or medical procedures, which then land on the mucous membranes of a susceptible individual within a short distance.
Mechanisms and Characteristics
Respiratory droplets are relatively large particles, typically greater than 5–10 micrometres in diameter, consisting of water, mucus and pathogens. Because of their size, these droplets travel only short distances—usually less than one to two metres—before gravity causes them to settle on surfaces or the mucosa of nearby individuals. This distinguishes droplet transmission from airborne transmission, in which smaller particles or droplet nuclei remain suspended and can travel longer distances. Conditions that increase droplet production include forceful exhalation, such as sneezing or coughing, and certain medical procedures like intubation. The risk of transmission depends on factors such as proximity to the source, duration of exposure, the amount of pathogen in respiratory secretions and environmental factors like humidity and ventilation. Viruses, bacteria and fungi that primarily spread via droplets often infect the upper respiratory tract, where they replicate and are shed. Droplets quickly lose moisture and may shrink in size, but they remain larger than droplet nuclei that can desiccate and behave like aerosols. Environmental conditions such as humidity and temperature influence evaporation and the distance droplets travel.
Clinical Examples and Prevention
Many common infectious diseases are spread primarily through droplet transmission. Examples include influenza, respiratory syncytial virus, Bordetella pertussis (whooping cough), Neisseria meningitidis (meningococcal disease), Streptococcus pyogenes causing scarlet fever or pharyngitis, mumps virus and rubella virus. Individuals contract these infections when droplets land on their eyes, nose or mouth, or when hands contaminated with droplets touch these areas. Because droplets do not remain suspended, interventions target close‑contact exposure. Covering coughs and sneezes with a tissue or elbow, wearing well‑fitting surgical masks, maintaining physical distance, improving ventilation and practicing good hand hygiene all reduce droplet transmission. In healthcare settings, droplet precautions include placing patients in single rooms or cohorting, and using masks and eye protection during procedures that generate droplets. Vaccination against pathogens like influenza, pertussis and rubella provides specific protection and reduces community spread.
Droplet transmission is distinct from airborne and contact routes, yet it remains a major pathway for many respiratory infections. Understanding droplet dynamics and applying appropriate preventive measures is key to controlling outbreaks and protecting vulnerable populations.
Related Terms: airborne transmission, contact transmission, respiratory droplets, aerosol, fomite