Why is the military taking pictures of sick people within the U.S?

Today I took my son to the doctors office because he hasn't been feeling well and when I got there there were many military officers not as patients there. They took his picture and several other ill peoples pics bec the gov requested it. l live in a small Nebraskan town and I have also noticed a greater presence of Military personnel. Why is this happening and why is the Gov taking pictures of sick people?