Slate (April 6) – The “gold standard” of rabies testing is testing the animal’s brain, including its cerebellum and brain stem, according to Dr. Leyi Wang, a veterinary virologist at the University of Illinois. If an animal has rabies, you will definitely find the virus in its brain.
https://slate.com/technology/2022/04/fox-capitol-hill-rabies-test-killed-good.html
Also in:
Smithsonian Magazine (April 8)
https://www.smithsonianmag.com/smart-news/rabid-fox-and-her-kits-euthanized-after-nine-people-were-bitten-on-capitol-hill-180979890/