On Elven Resistance to Disease

Elves are not immune to disease. They do, however, possess immune systems sufficiently different from those of Humans that the distinction has repeatedly been exaggerated into myth. Certain Human illnesses infect Elves poorly, and others produce only mild symptoms. Several common childhood diseases which once killed large numbers of Humans appear to pass through Elven populations with little effect, which has encouraged the belief that Elves are generally resistant to infection.

Unfortunately, the diseases to which Elves are vulnerable are often the ones Humans fail to recognise. Elven fevers may progress slowly, linger for weeks, and produce subtle organ damage before the patient appears seriously ill. Their strong regenerative capacity can also disguise the severity of tissue injury until the underlying disease is already advanced. Thus an Elf may look healthier than a Human under comparable physiological stress, which is not the same thing as being healthier.

There are also pathogens adapted specifically to Elven biology which Humans barely notice. One common woodland fungus produces no more than an itchy rash in Humans and can cause severe systemic illness in Elves. Nature is very egalitarian in this respect, and finds ways to inconvenience everyone.