Carl Zimmer in his blog, The Loom:
You may have heard last month’s news about an aggressive form of HIV that had public health officials in New York scared out of their professional gourds. They isolated the virus from a single man, and reported that it was resistant to anti-HIV drugs and drove its victim into full-blown AIDS in a manner of months, rather than the normal period of a few years. Skeptics wondered whether all the hoopla was necessary or useful. The virus might not turn out to be all that unusual, some said; perhaps the man’s immune system had some peculiar twist that gave the course of his disease such a devastating arc. But everyone did agree that the final judgment would have to wait until the scientists started publishing their research.
Today the first data came out in the Lancet. One of the figures jumped out at me, and I’ve reproduced it here. The scientists drew the evolutionary tree of this new strain. Its branch is marked here as “index case.” The researchers compared the sequence of one its genes to sequences from other HIV strains, looking to see how closely related it was to them. The length of the branches shows how different the genetic sequences are from one another. The tree shows that this is not a case of contamination from some other well-known strain. Instead, this new strain sticks way out on its own.