This has a really gripping beginning, the first paragraph is really wonderful! It's a beautiful way to hook a reader! There are just a few things I'd like to point out, though.
The forth and fifth paragraphs don't make sense. The first sentences of each those paragraphs, specifically. Just re-read those two paragraphs and see if you can make them flow right- something about them doesn't seem natural.
The fact that you said "9mm pistols" and didn't actually spell out the words kind of annoy me as a reader, but maybe that's just me. You do this throughout the whole thing, and seeing random numbers on my page is really distracting.
Speaking of numbers, there's one point when you say "27 pouches of water strapped on my back." Maybe you should consider changing this to something not so specific. Most people, when fighting for survival, probably wouldn't think exactly how many packs of water they have. They're just thinking "Do I have enough to survive?" or "How long will this last me?"
Other than these few things, this was really well written! I love how you talk about Carriers but never actually talk too much about the infection itself. Vagueness is a very important aspect in any story that has to do even slightly with fear, since every human being does, after all, have a fear of the unknown.