U.S. military doctors learned early on in Afghanistan that the smallest cut could quickly turn into a serious infection. So the policy has been to warn the troops to get a large dose of antibiotics for the slightest scratch. The reason is simple; sanitation is primitive in that part of the world and the constantly blowing dust tends to contain fecal matter. The concept of outhouses and field latrines (a hole in the ground, covered over after the troops have filled it up) never caught on it a big way. So there's plenty of infectious crud in the air. Afghans are also susceptible to this, but with an average lifespan of about forty years, only the strong (infection resistant) survive. But even sturdy adult Afghans can get bad infections, so Special Forces medics find that carrying a large stock of antibiotics will win Americans friends.