Foster kittens keep getting resident cats sick?

Hi, I've been fostering for awhile now and it seems like every litter from shelters in the area always has something contagious, whether URIs or parasites or fleas, and even when I think I'm being cautious my adults end up catching things. I'm extremely careful about the spread of germs, the kittens are kept in their own room of course, with an extra barrier on the outside so my adult cats can't get too close to the door. I don't let ANYTHING go between the kitten room and the rest of the house that can't be thoroughly washed, I make everyone who pets the kittens wash hands and change clothes between rooms, sometimes I put my adults on lysine supplements to try to prevent them catching anything, and my adults still always end up catching something from every foster cat. I know some germs just can't be killed easily, like coccidia is the current problem and I know that's nearly impossible to kill with common cleaners. I love fostering, but it's just getting to be too much stress when my cats catch things, and I feel terrible exposing my 15 y.o. male to all these illnesses (not to mention vet bills...) is there something else I should/could be doing to minimize the spread of illness from the kittens to my cats?

i have the same problem right now. i had a litter of 4 foster babies with severe diarrhea that turned out to be coccidia and all 4 of my cats got sick and we are still fighting it a month later. we just went back to the vet and he said he didn't see anymore coccidia but there is some other parasite. ggrrr! this litter has cost me a fortune in vet bills, cleaning supplies, medicine, special food etc...

my husband doesn't want to foster anymore because of the risk to our cats. i want to keep doing it but i may stick to healthy adults instead of kittens.

Oh no I'm so sorry to hear that!! I'm hoping our coccidia issue doesn't take so long to get rid of... I fostered an adult last year who had fleas that my cat caught, so they may not be totally risk free either. Though at least fleas is a pretty benign issue to get rid of since it only took one round of flea treatment to clear them both up.