Terrence Fugate wrote:

>  The average American who isn't symptomatic might have the common cold
> and/or flu that hasn't gone active, they could have latent syphilis
> and, if they had chickenpox, the herpes zoster virus would be hiding
> in the nerves likely to 'awaken' when they get old enough for their
> immune system to weaken as shingles.
>
>  He would not be a likely carrier of any serious biological disease
> but his intestinal flora would very different from the locals of
> Hostigos. This could create GI upset for everyone as they traded
> e-coli. [Trust me, you really don't want to think about how often we
> trade e-coli.]

But what constitutes a serious biological disease in Hostigos? Measles,
German measles, whooping cough, mumps, the common cold might have a
major lethal effect on a population that lacks the benefits of endemic
exposure.

Just look at what happened in our timeline when Venusian Swamp Fever got
loose in 1918.