[mcdoh]

> In fact, health officials say the virus is so contagious that if an unvaccinated person walks through a room two hours after someone with measles has left, there’s a 90 percent chance that an unvaccinated person will get the disease. People can spread measles for four days before the rash appears and for four days after.

Yikes!

[Fomite]

Seriously. I'm an infectious disease epidemiologist, and measles is amazingly transmissible.

[Johnny555]

As an infectious disease epidemiologist, could you elaborate on that? What is it that makes it so contagious?

[Fomite]

A couple reasons:

- 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.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4997572/