Meryl says “one at a time now”

In the magazine she publishes (Informed Voice, Winter 2006, page 48), Meryl wrote:

It is a fact that we will only ever contract one disease at a time

I guess that will come as suprising news to anyone who has ever contracted pneumonia as a complication of flu, or any of the usual complications that go with AIDS (caused by HIV), to name just two examples. Oh Meryl!