Typhoid Mary?

Disease vectors are not always obvious. Rats, fleas, bacteria, people, water and the list goes on. Typhoid Mary is an interesting example. A carrier but not a victim. The difficult in a epidemic is to understand how the disease is transferred. It may not be linear and it may not be from one sick person to another.

As we understand immunology today, we should be able to determine if someone was exposed. There should be an antibody at the very least and testing for that antibody is well within the realm of our day to day abilities. However one wonder two things. In a residence with an outbreak, why not test everyone there or who has been there? Second, and yes this goes against all we know, is it possible for a carrier not to exhibit an immune response?

Like AIDS, perhaps this may add new light on our immune systems.