Since the cause of the illness is not known, the question of contagion is n=
ot known.
Many studies suggest that there is no correlation between CFS and casual or=
 intimate
contact. On the other hand, there are infrequent but occasional reports of =
cluster
outbreaks of CFS. How that can happen, while at the same time in other inst=
ances
intimate family members do not pass on the disease, remains one of the myst=
eries of
this illness.