OK, I also have to admit to one tiny personal disappointment with The Girl With All The Gifts. It is possible that what I am about to discuss could be considered a spoiler, so proceed at your own discretion. Also there are mildly gory true-life biological experiment details involving animal subjects below.
Back in high school, I worked on a toxicology study for a summer. We were working to answer a certain question about delayed neurotoxins (i.e. organophosphates). Typically, after being exposed to delayed neurotoxins, vertebrates such as chickens, cats, ferrets, mink, and humans experience progressive neurological impairment over the course of days or weeks, especially of their back or lower limbs.
In chickens at least, however, immature chicks seem to be immune to the effects of this class of delayed neurotoxins. At the time, nobody knew why. Was it because their digestive systems were too undeveloped to absorb the toxins? That was one hypothesis.
So we bypassed the digestive system entirely by injecting organophosphates into days-old chicks intravenously, intramuscularly and intraperitoneally. Plus the control group, of course.
Then we pureed their brains (not all of them, only 50%, just like Dr. Caldwell) and tested them for the presence of neurotoxic esterase (NTE), an enzyme which would indicate that the compound had been absorbed and metabolized.
NTE was present in all the dosed chicks. The chemical was absorbed just fine. So we watched the other half of the chick population for limb impairment over the course of a month or so.
The compound was swimming around in the chick's bodies; it just wasn't having any effect on their nervous system.
JUST LIKE THE KIDS IN THE BOOK, Y'ALL.
Except not, because instead there's this thing about first-generation zombies having sex with each other and then gestating babies that I frankly find strained my suspension of disbelief so hard it still has stretch marks. Oh well.
P.S.: Effect of route of administration on the development of organophosphate-induced delayed neurotoxicity in 4-week-old chicks.
Olson BA1, Bursian SJ.
Department of Animal Science, Michigan State University, East Lansing 48824.
J Toxicol Environ Health. 1988;23(4):499-505.https://www.ncbi.nlm.nih.gov/pubmed/3361617