- While it enters via the lungs, the virus emerges in the trachea, which positions it really well to be aerosolized through coughing. This aerosol and droplet transmission is really efficient.
- Measles is relatively stable in the environment, so lingers for a fair amount of time.
- It also appears to have a relatively small infectious dose.
Other highly contagious diseases, like norovirus, share fairly similar properties - you make a lot of virus, it hangs out for awhile, and you don't need to come in contact with much of it.