I'm not sure where the best resources to read are, I studied biology and am going off of existing knowledge.
ALL pathogens if they can penetrate the skin get access to a body and can cause infection. Simple as that.
All pathogens aim for is to harvest your cells. Bacteria and single-cell eucaryote will digest and eat your cells. Viruses will go inside your cells and reprogram cell produce new virus particles.
It is that simple and the easiest way to our bodies is through mucus membranes as they lack skin and are protected by a thin layer of mucus, in other word slime and snot. You have mucus membrane in your aerial pathways in your head as eyes, nose and mouth. Also, your lungs are the huge surface area of mucus membrane.
But if your skin for any reason is ruptured it opens access for any pathogen go in that way. Point is if a pathogen has access to your cells or not. Nothing else. Most infectious diseases first get inside of your body via mucus membranes.
Our skin is not only that last layer of the nonliving layer but consists about few inches of separate layers that in microbiological points are just layers of defense against anything that tries to invade the body. Blood vessels are thin, cell walls that allow white blood cells to move between layers. All layers have little living cells as possible and cell types that are hard to use as food.
So if the skin is only damaged it still gives a fairly difficult pathway to pathogen get on without ending with a good fight. If the skin is fully penetrated the situation is different. That's why all deep penetrations to tissues often cause so severe infections. As whatever pathogen with an arrow, knife blade or bullet get deep in a body where is easy to spread and defenses are low.
My posts have been downvoted into oblivion by a bunch of programmers, but ask a doctor if what I'm saying is correct or not. It is.
