The 25 days to go entry of Countdown focuses on a sweet moment between Stacy Mason, her son Philip, and the adorable golden retriever from next door. Heart-wrenching knowing what Georgia told us in Feed about Philip, the dogs, and Stacy. Doubly so because Seanan McGuire posted the '25' snippet going into Mother's Day Weekend 2011.
T-8 Suzanne Amberlee, grieving for her daughter Amanda, succumbs to the Kellis-Amberlee virus and starts the Denver Outbreak, at a playground.
T-1 Marigold the Golden Retriever is a good dog who doesn't want to be called a bad dog.
Georgia's final blog post in Feed. Typing it out in desperation as the virus kills her humanity and her last typed words are keyboard smash gibberish interspersed with her begging her brother to shoot her. Oh, and also interspersed is her telling her brother she loves him.
Not only does Georgia die telling Shaun she loves him, the fact that she loves her brother is the last thing she remembers before the virus takes hold. She forgets her own name before she forgets that she loves Shaun.
For animal lovers, the death of Rick's beloved cat, Lois, especially in light of all the losses he has already suffered. The way he keeps asking why somebody would kill "such a little cat" while sobbing really makes the reader's waterworks flow. Also him clutching Lois' dead body to his chest as he's running from explosions and KA-containing darts.
Kelly's whispered admission to Shaun that she would have gotten better, meaning Georgia would likely have survived amplification of the virus and not zombified, so Shaun did not necessarily have to shoot her, which causes him even more significant and severe Sanity Slippage.
Blackout:San Diego 2014:
The sequence when Lorelei calls her parents in hysterical tears to warn them that the authorities are writing off the convention center without attempting rescue.
and the final sequence of the narration of the events: It's described to the reader in neutral, general terms, but to any fan of Firefly and/or Serenity, there is no mistaking that the song the Browncoats are singing is the Theme Tune, "You Can't Take The Sky From Me".