system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Can I get sick from myself?

If I am sick and eat out of say a peanut butter jar straight out of it with a spoon and a week or so later when I'm no longer sick eat out of the same jar can I get myself sick again?
gpt
If you are sick from viral infections: no.

The immune system works in a way that it builds immunity from previously encountered viral pathogens. This prevents you from getting sick from the same flu strain a week after it has cleared your body.

If you are sick from a bacterial infections: yes.

When you put e.g. diarrhea causing bacteria on your food and eat from it a week later you might get sick again with the same infection. These bacteria could be in your stool and get onto your hands and transferred to your food.