A new strain of the botulinum toxin - the most acutely toxic poison on Earth - has been found in California in a child suffering from botulism.
There is no antidote to the new toxin - the first to be found in more than 40 years, and it has sparked fears the substance could be misused as a bioweapon.
Inhaling 10 nanograms of the toxin would be enough to kill an adult - and for the first time in history, scientists have withheld publication of its DNA sequence until an antidote can be found.
The toxin, produced by a bacteria, is similar to other types used in minute quantities in botox injections - but in larger doses these cause paralysis, and can kill in hours.
Researchers fear that if the new type H's DNA sequence were published, it could be used to cause "widespread harm."
[False widows are probably false alarm]
“The 7 botulinum toxin types A–G were discovered between 1897 and 1970,” the researchers, Jason Barash and Stephen Arnon of the California Department of Public Health, write.
“This new toxin, H, cannot be neutralized by any of the currently available antibotulinum antisera, which means that we have no effective treatment for this form of botulism,” the researchers write.
“This is the first new botulinum toxin type to be recognised in more than 40 years,” the researchers write. “Mice injected with stool extract plus antitoxin A died within 24 hours, while mice injected with stool extract plus antitoxin B died within 48 hours.”
Tests with antitoxins from the U.S. Army failed to neutralise the new toxin in tests on mice - there was some success with antibodies grown in rabbits, but not enough to produce an effective human antidote.
The researchers have withheld publication of the gene sequences for the new toxin until an antidote becomes available.
"Because no antitoxins as yet have been developed to counteract the novel C. Botulinum toxin, the authors had detailed consultations with representatives from numerous appropriate US government agencies,” the researchers wrote.
“Modern knowledge of Clostridium botulinum originates with the discovery of the bacterium in 1897 by van Ermengem, who isolated it from an incompletely salted ham eaten in the now-famous foodborne botulism outbreak in the small Belgian town of Ellezelles that sickened 23 members of a musical club, of whom 13 became quite paralyzed and 3 died.”
The researchers say that the “possiblity of misuse” left them with a difficult dilemma - and say that it serves as a reminder that new strains “likely await discovery.”
“Until an antitoxin can be created, shown to be effective, and deployed, both the strain itself and the sequence of this toxin (with which recombinant protein can be easily made) pose serious risks to public health because of the unusually severe, widespread harm that could result from misuse of either,” David Relman of Stanford University writes.
”The dilemma faced by these authors, and by society, revolves around the question, should all of the information from this and similar studies be fully disseminated, motivated by the desire to realize all possible benefits from the discovery, or should dissemination of some or all of the information be restricted, with the goal of diminishing the probability of misuse?”