Why are they sick

Okay moms I feel alone my son 2 years old got sick yesterday morning random thowing up 2 times look white and by noon he was fine .. Now my one year old has a fever. Like what the f#!$# why and how ??we dont go out so where and why are they getting sick with no other symtome. And noone comes and goes from the house. I just want to cry cuz I'm just tired of hearing about covid and when my kids get sick with no reason makes me just get scared and wonder.. 😭 I just need help with the kids but how when I cant because of covid .. I feel so alone 😢