This paper supports my idea that many of us, specially those that are very thin, may have an unconscious fear of infection, or antibiotics that we got from an infant infection and or overuse of antibiotics.
This unconscious fear of infection may be a greater part of our makeup than we thought.
In the paper, the scientists go through a list of common symptoms, and each seems to support the hypothesis that feeling sick is an evolutionary adaptation. Appetite loss, for example, hinders the disease from spreading by communal food or water resources. Fatigue and weakness can lessen the mobility of the infected individual, reducing the radius of possible infection. Along with the symptoms, the sick individual can become depressed and lose interest in social and sexual contact, again limiting opportunities to transmit pathogens.