What type of disease?

So I was watching World War Z (Again) and Jerry (the mc) injected himself on vial of disease in order to make him invicible to the zombies or infected.

So in the WWZ universe in order for you to camouflage from the infected you have to be terminally Ill or just have a very very deadly disease inside of you. So I was wondering what did you think Jerry injected with himself? And if so why didnt he die from it? Thank you