Measles Transmission Mode
Measles is transmitted via the airborne route, making it one of the most contagious infectious diseases, with the virus capable of remaining suspended in air for extended periods and traveling long distances to infect susceptible individuals. 1
Primary Transmission Mechanism
Airborne transmission is the predominant mode by which measles spreads, distinguishing it from typical droplet-transmitted infections. 1 The measles virus (rubeola) becomes airborne in small-particle aerosols that can:
- Remain suspended in the air for prolonged periods (at least one hour after an infected person leaves a room) 2, 3
- Travel over longer distances beyond the typical 3-6 feet associated with droplet transmission 1
- Infect individuals who never had direct face-to-face contact with the source patient 2
Evidence from Outbreak Investigations
The airborne nature of measles transmission has been definitively demonstrated through multiple documented outbreaks:
- Office-based transmission studies showed children contracted measles despite arriving 60-75 minutes after the infected child had departed, with no direct contact occurring 2, 3
- In one pediatric office outbreak, 3 of 7 secondary cases occurred in children who were never in the same room as the source patient 2
- Airflow studies in these settings demonstrated that droplet nuclei generated in examining rooms were dispersed throughout entire office suites via recirculated ventilation systems 2
Household Transmission Context
In the scenario presented with multiple siblings affected, airborne transmission explains the high attack rate within households. 1 Among unimmunized individuals exposed to measles, over 90% will develop disease, reflecting the extraordinary efficiency of airborne spread. 1
Clinical Implications for Infection Control
The airborne nature of measles transmission requires specific precautions:
- Airborne infection isolation rooms (negative pressure) are mandatory for suspected or confirmed cases 1
- N95 respirators (not simple surgical masks) are required for all healthcare personnel entering patient rooms, regardless of immunity status 1
- Infected individuals remain contagious from 4 days before rash onset through 4 days after rash onset 1
Why Not the Other Options
Droplet transmission (Option B) is incorrect because while measles virus is present in respiratory secretions, the virus becomes aerosolized into particles small enough to remain airborne for extended periods, exceeding the definition of droplet transmission. 1
Fecal-oral transmission (Option C) is not a recognized route for measles, which is strictly a respiratory pathogen. 1
Bloodborne transmission (Option D) does not occur with measles; the virus spreads through the respiratory route exclusively. 1
Common Pitfall
A critical error is confusing measles with pertussis or influenza, which are primarily droplet-transmitted infections. 1 Measles is specifically categorized alongside varicella and tuberculosis as requiring airborne precautions due to small-particle aerosol transmission. 1
Answer: A. Airborne