In the two or three years since "krokodil" has come to public attention, it has continued to spread, and as of October of this year, there are reported cases in the United States that may or may not be "actual" krokodil.
But lets talk about what "actual" krokodil is. The drug behind krokodil is desomorphine, a slight alteration to the morphine structure that has slightly different effects. Structurally speaking, the only different between morphine and desomorphine is the removal of a single hydroxy group. This makes the drug more powerful on a weight for weight basis, and also makes it have a shorter onset of action and a shorter duration of effect. Clinical research on the differences between desomorphine and morphine seem to have mixed results. But the basic science is that there is nothing especially insidious about desomorphine itself, and that for certain uses, it could be a very therapeutically useful drug.
The difference between desomorphine and krokodil is the refining process, which is not very refined. The street drug includes various chemicals used in the manufacture, which can cause extreme skin lesions, especially combined with unsanitized needles that carry infectious agents, especially MSRA. The only specific way that desomorphine makes this worse is that its short duration of action means addicts need to inject more frequently. But desomorphine itself doesn't lead to skin lesions or necrosis anymore than injection with shots of Thiamin would. And it seems that many (or all) of the reported cases of "krokodil" tissue damage in the United States were "just" heroin.
Although it is a complicated issue, krokodil does strengthen arguments for harm reduction approaches in my mind. Opiates can be very dangerous, but they are usually not toxic. They certainly do not cause tissue damage on their own. They are also not hepatotoxic. But since they are illegal, addicts are driven to take more and more dangerous forms of the drug. While there are good reasons to keep opiates illegal, they should be balanced against the horrific unintended consequences of users being driven to take drugs like krokodil.