For a slight majority of patients, the illness begins suddenly as though on=
e had come
down with the flu. Except that this "flu" doesn't seem to completely go awa=
y. For many
other patients, the onset appears gradually over a long period of time.

In many cases, a high-stress event seems to "trigger" the illness. There ar=
e many cases
in which CFS appears to have begun with a severe head injury, for example. =
But since
such events seem to have no apparent logical connection to the illness that=
 follows,
many have speculated that the CFS was latent in people beforehand in these =
cases,
and that the stress of trauma merely triggered the stress-hypersensitivity =
aspect of the
illness. Some have further speculated that other stressful factors in our e=
nvironment, be
they microbes or pollution, may also prompt this illness to bloom.