When I try to quantify the contagiousness of diseases, I always use measles as an example of extreme contagiousness. On stage giving lectures, I tell the audience that if I had measles they would all be exposed. Fortunately many were lucky enough to be vaccinated as children and grow up in an era with high levels of immunization, conferring the protection of the herd (i.e. herd immunity).
However, largely due to the efforts of the anti-vaccine movement, there are pockets of this nation in which immunization levels have fallen to levels that have fostered the return of this dread disease that causes pneumonia in 1 of 20 who contract it and kills at a rate of 1 per 1000.
One of these pockets happens to be California which is currently in the midst of its worst measles year in two decades. Making matters much worse for California is the report that approximately one dozen cases of measles have been reported to be linked to exposures at Disneyland. Of the original cases reported, half were unvaccinated despite being eligible for vaccination.
To measles, Disneyland is a viral-exchange center in which it will gain access to individuals from all over the world some of who may not be vaccinated because of their parents' (deadly) choices, some because they are too young, and some whose immune system precludes it. From Disneyland, the virus can be carried to other states and nations.
The anti-vaccine movement has now made Disneyland the happiest place on earth--not for the children of the world--but for a wretched virus.