Two thoughts on this - one is that if she has anthrax the CDC ought to be all over Star Labs, it's taken very seriously; and she may have been spreading it wherever she goes! Larry is especially at risk, I think. The other is that we still don't know how she was exposed to the disease - I somehow doubt that Larry is the source, but presumably she's picked it up somewhere.
Someone who knows more about anthrax than I do may be able to shed more light on this.