Why does no antitoxin for botulinum type H exist yet?
The premise of this question is based upon outdated information.

According to Study: Novel botulinum toxin less dangerous than thought


  Researchers from the Centers for Disease Control and Prevention (CDC) and the University of Wisconsin (UW), writing in the Journal of Infectious Diseases (JID), said it turns out that the novel toxin can be blocked by available antitoxins after all. That suggests that it isn't really a novel toxin, the authors said


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