Acute mild activation of the immune system via typhoid injection can lead to feelings of social isolation and dysphoria, and changes in brain function associated with depression.

“So the folks in London, Hugo Critchley’s group, they tended to use typhoid, and they showed that right, you know, you give normal folks a shot of typhoid which activates a sort of acute mild, it’s not going to interferon is like a sledge hammer, right? I mean this is more like a, like... But you do that and you got people report feeling more socially isolated, they feel more dysphoric, and you see changes in their brain that sort of speak to depressive brain functioning.”