If you have ever wondered why recovering from sickness makes it seem worse than the actual condition, science has an answer.
According to researchers, the answer may lie in a component of the immune system known as the acute-phase response during an invasion by bugs, viruses or microbes.
This response puts healthy cells and tissue under tremendous stress, and is actually the cause of many of the symptoms tied with feeling sick, the journal The Quarterly Review of Biology reported.
Acute-phase response raises body temperature, causes mild anaemia and loss of appetite.
Certain vital nutrients, namely, iron, zinc and manganese are partially sequestered away from the bloodstream.
"The question is why would these harmful components evolve," said Edmund LeGrand from the University of Tennessee, who co-wrote the paper with Joe Alcock from the University of New Mexico.
The researchers said the answer becomes clear when the acute-phase response is viewed in terms of what they called "immune brinksmanship", according to a Tennessee statement.
LeGrand said the concept was akin to what happens in international trade disputes.
When one country places trade sanctions on another, both countries' economies take a hit, but the sanctioning country is betting that its opponent will be hurt more.