<p>A frightening immune disorder turns out to be rare and noncontagious
</p>
<p> Has a new strain of the AIDS virus emerged, threatening to ravage
the world like its better-known cousin? That looked possible
last summer, when scientists at an international AIDS conference
reported on patients who had strikingly low levels of CD4 cells--the same immune-system cells that are destroyed in AIDS sufferers--but were not infected by the HIV virus.
</p>
<p> The mystery triggered a flurry of research, and the results
are just in. The disease isn't AIDS, says the New England Journal
of Medicine. It seems to be noncontagious, it's rare and likely
to stay that way, and it probably has a variety of causes. The
possible culprits include bacteria, fungi and other parasites,
poisons and environmental toxins. Viruses may play a role as
well, but not necessarily a single virus or even a family of
them. In a Journal editorial, Dr. Anthony Fauci, chief of U.S.
AIDS research, called last year's press speculation about a
new AIDS virus a "media frenzy" that was "inappropriate."
