February 21, 2012 “What scares me is that this could happen and this could happen so easily”
….air flowed into the next cage. killing all 40 exposed ferrets.
The above comments are from an ABC news video report on the H5N1 transmission experiments by Ron Fouchier in the Netherlands. His quote above highlights his concerns and the second comment highlights the level of lethality seen for the H5N1 that was used to infect one of the ferrets which maintained its high level of lethality after acquiring the full set of 5 changes in 2 genes. This level of lethality was in marked contrast to experiments by Yoshi Kawoaka which also achieved efficient transmission in ferrets but failed to kill at levels higher that H1N1pdm09, which was used as a genetic background for the H5 gene.
Thus, two very different approaches were used to achieve efficient transmission by H5N1 with natural acquisitions, raising serious concerns that such changes could lead to a catastrophic pandemic. However, recent debate has been more focused on H5N1 as a bioweapon, or a true case fatality rate that is orders of magnitude lower than the 60% CFR in confirmed cases.
However, the above ferret studies indicate the H5N1 from Indonesia (Fouchier experiment) is far more lethal than the Vietnam H5N1 H5 reassortant (Kawaoka experiment), and those citing a lower CFR based on serological studies are the same scientists downplayed the ability of H1N1pdm09 with a truncated F2 gene or an acquired receptor binding domain (RBD) change, D225G.
The prediction that the F2 truncation would limit H1N1pdm09 spread was not supported by subsequent events. The virus quickly spread worldwide and then began to appear in additional species (most notably swine and birds), raising concerns for reassortants similar to the virus used in the Kawaoka experiments. Similarly, the claim that D225G would not transmit in humans was based in earlier experiments targeting two RBD changes (E190D and D225G). However, D225G was found in approximately 40% of 1918 sequences, supporting transmission, as well as seasonal H3 sequences from the mid-1990’s, which also was present on H3N2v sequences, including the West Virginia cluster, which included 23 contacts with ILI, again supporting D225G transmission. This transmission is also supported by the Kawaoka and Fouchier experiments, because virtually all H5N1 sequences have D225G.
Thus, the predictions by those citing a low case fatality rate for H5n1 are the same “experts” who discounted the effects of H1N1pdm09, and who cite weak serological data which may be detecting cross-reactive antibodies ro those induced by low path H5.
The death of all 40 ferrets by the Indonesia H5N1 highlights the need for an aggressive H5 vaccination campaign, instead of distractions by unlikely bioterrorism, or claims that H5N1 lethality is largely over-estimated.