Well I kept on living for quite a few hours, finally found some antibiotic but that didn't do much. Sick status was now a dark orange with some times the message "I'm feeling run-down" or something similar. After a long run in to town I got the message "I'm feeling tired". All the time I was hydrated and well fed. Screen color stayed completetly black and white with no change.
Unfortunately I ran in someones barrel while looting a city building and was killed on sight (pfff).