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Fujian H5N6 Cases In China Raise H5N8 and H5N2
The patient, who is in critical condition, is currently receiving treatment in a hospital in Guangzhou. No abnormality was reported among the close contacts of the patient.
The above comments describe the second H5N6 reported case. The first case was fatal and in Sichuan Province in April, 2014. A full set of sequences, A/Sichuan/26221/2014, has been deposited at GISAID by the WHO Chinese National Influenza Center in Beijing. The H5 is Fujian clade 18.104.22.168 and the six internal genes have an H5N1 lineage. Markers associated with mammalian adaptation are T160A in H5 and D701N in PB2. In China, the vast majority of human H7N9 cases have PB2 E627K, and the majority of PB2 sequences lacking E627K have D701N, suggesting PB2 in bird flu sequences are a mixture and the rapid appearance of E627K or D701N represents strong mammalian selection pressure.
The reporting of two H5N6 cases in China in 2014 raises concerns that additional human cases of Fujian clade 22.214.171.124 will be reported, including H5N8.
In recent years several sero-types with Fujian clade 126.96.36.199 have been reported, including H5N1, H5N2, H5N6, and H5N8. The H5N8 has been a concern because it is currently circulating in Europe (Germany, Netherlands, England, Italy) as well as Japan, with transmission via wild birds.
This transmission has led to the first reports of Fujian clade 188.8.131.52 in North America, including H5N2 (see map) in Canada (British Columbia) as well as H5N8 (see map) and H5N2 in the United States (Washington and Oregon). The H5N2 has five H5N8 gene segments including Fujian clade 184.108.40.206.
A recent paper on H5N8 described a mixed receptor binding preference for both gal 2,3 and gal 2,6 receptors and the presence of T160A, which abolishes the glycosylation site at 158N, as a reason. In H5N1 gain of function studies , passage in ferrets led to the abolishment of this glycosylation site as a prerequisite for ferret to ferret transmission.
Thus, the reports of human cases of H5N6 in China raise concerns that there will be H5N8 and H5N2 cases in areas impacted by these outbreaks.