I know the drill, I worked as an EMT for 3 years. The chance of a random car accident victim having some chronic easily transmitted disease is tiny. Even then you are more likely to end up with the residue on you from multiple patients being an issue to other immunocompromised patients than them being a threat to you.
If you work in health care your dozens of patient contacts make you likely to transmit disease on your skin/clothes that your body can resist but a patient cannot.
Make sure you adjust the kit depending upon weather. Summers are brutal here, so we carry a gallon of water per person, minimum. They get checked weekly, along with anything else that’s heat sensitive.
It’s not really first aide, but an extra pair of shoes is a good thing to have.
I travel around the world a lot, often to developing countries. I carry two medical kits. One is first aid and the other is pharmaceutical.
The first aid kit to my memory has bandages, scissors, disinfectant wipes, some safety pins and and I’ve added a couple of packaged syringes and needles. Can’t remember what else - I’ve had it since 2004 and have never had to use it.
The pharma kit, which gets dipped into all the time, has:
Two full courses of generic antibiotics (amoxicillin)
One full course of metronidazole
Chlorpheniramine
Domperidone
Loperamide
Aspirin
Acetominophen
Acetominophen + codeine tablets
Ibuprofen
Terbutaline sulphate
Electrolyte powders
White flower oil
Topical antibiotic cream
Vitamin C
Band aids of various sizes
Growing up as a kid, my mother had her medicine kit for us kids in the bathroom:
Band-Aids
Aspirin
Pink Lotion (aka calamine lotion)
Years later, we would joke that if we came home with a broken arm and one eye hanging out of the socket, all we needed was to rub some pick lotion on the arm, take an aspirin and use that Band-Aid to hold the eye until it healed.