My family and I have swine flu- why aren't we sick?

I took my son in to the dr today because he had his first ever ear infection (he'll be 3 next month). There they were testing everyone for swine and he came up positive. My kids, ages 5, 2, and 1 all had a slight fever 100 degrees 5 days ago for 24 hours. Their appetite and temperment never changed and they all have a cough but that's it. My husband and I have to have swine flu as we kiss them all the time and I share my yogurt and eat the the food they don't eat, as well as share water,etc.. My throat glands were feeling a tad sore but I didn't even notice until my son was diagosed today and I've been a tiny bit more tired. I don't have a cough either. They only reason I can come up with is maybe our immune system is strong? My husband and I are extremely active, run 3 miles a day and we eat very healthy, mainly veggies and no processed foods. Any suggestions as to why we remain relatively unaffected?