How does measles spread?

How Measles Spreads

Measles is a highly contagious viral disease that is transmitted primarily through respiratory droplets and airborne spread when infected individuals cough or sneeze. 1

Transmission Mechanisms

• Respiratory route: Measles virus spreads through:

  • Respiratory droplets (particles >5μm)
  • Airborne small-particle aerosols that remain suspended in air 1
  • Direct contact with infectious respiratory secretions

• Highly contagious nature:

  • Infected persons are contagious from 4 days before rash onset through 4 days after rash onset 1
  • The virus can survive in airborne form for at least one hour after an infected person has left an area 2
  • Measles is one of the most contagious infectious diseases, with attack rates approaching 80% in unvaccinated individuals exposed to the virus 2

Evidence of Airborne Transmission

• Studies have documented measles transmission occurring without direct contact with infected individuals:
  • Cases have been reported where individuals contracted measles despite only being in the same building as an infected person without face-to-face contact 2
  • In one documented outbreak, children contracted measles despite arriving at a medical office an hour after an infected patient had already left 2

Risk Factors for Transmission

• Unvaccinated status: Individuals without immunity through vaccination or prior infection are at highest risk
• Enclosed spaces: Modern building designs with recirculated ventilation may increase risk of airborne transmission 2
• Healthcare settings: Particularly high-risk environments where infected patients may expose vulnerable individuals 1

Infection Control Measures

When a person with suspected measles visits a healthcare facility:

1. Immediate isolation precautions:

   • Patient should wear a medical mask
   • Place in negative-pressure airborne infection isolation room
   • If isolation room unavailable, use private room with door closed 1

2. Healthcare personnel protection:

   • Only staff with presumptive immunity should enter the room when possible
   • All staff should use N95 respirators or equivalent respiratory protection regardless of immunity status 1
   • Healthcare workers with measles should be excluded from work until ≥4 days after rash onset 1

Global Impact

• Before vaccination programs, measles was nearly universal in childhood with an estimated 3-4 million cases annually in the US alone 1
• Despite elimination in some regions, measles remains endemic in many parts of the world with approximately 20 million cases occurring worldwide 1, 3
• The virus is strictly human with no animal reservoirs, making it theoretically eradicable through vaccination 3

Understanding the highly contagious airborne nature of measles transmission is crucial for implementing effective prevention and control measures, particularly in healthcare settings where vulnerable populations may be exposed.