Kate calls herself "an expendable." She tells us in the first few paragraphs she expected to die in a lab accident, and was told this from when she was ten years old onwards. Everyone in InfecSec is absolutely okay with being told they will likely be killed quickly in this field, even the ones like Taylor, who are considerably more ordinary than Kate.
The Davis-McLean family. The cousins' parents and Kate's father are dead, and Sharon and Joe are completely irresponsible and neglectful if not outright abusive. Even Kate, who is usually strong-willed and inquisitive, knows there are some things that you do not ask Joseph McLean. She seems somewhat frightened of him, and she's not frightened of infected corpses. What is he doing to these kids when he's drunk?!
Cosette's life is worrisome too. Scout is lazy, we haven't even seen Scarlett or Tim yet, Taylor is immature, and Kate is brilliant but god-awful at acting normal. Anna is still young, only 15, and is single-handedly raising a child! Who knows how that affects her and Cosette?
Kate is very isolated and very asocial. She has no friends to speak of, no meaningful relationships, and the only people who actually seem to care about her are Taylor and her cousins- not even her own mother. There is almost no human interaction in her life outside of a few of her family members, and they're not super involved in it at all. Imagine being a teenage girl in a world where no one is close to you, ever. No wonder she bottles up her feelings.
The teens working in the lab don't really seem like the most stable individuals. Taylor cries at the drop of a hat, and doesn't care about the work at all. Kate is apathetic and antisocial, and is bad at communicating. Rich outright says he's on the verge of a nervous breakdown. Taylor is disliked because her teammates find her irritating, Kate is thought of as weird and an outcaste, and teen drama rules Dana and Lucille's lives. Not one person here should be working with diseases that could wipe out a planet.
Kate's absolute respect and love for these diseases is kind of worrisome.
Everything about InfecSec. Not only do these teenagers have serious potential to kill themselves, they could possibly take everyone else along with them. Tigris outright plays this straight- one teenage girl doomed humanity because she panicked in a lab.
