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Novel H7N9 In Hong Kong Infant Import from
Her nasopharyngeal aspirate tested positive for avian influenza A(H7N9) virus upon laboratory testing by the CHP's Public Health Laboratory Services Branch today.
The patient has been sent to Princess Margaret Hospital for isolation. Her current condition is stable.
The CHP's initial investigation revealed that the patient had been taken to a wet market in Shenzhen by her grandparents four to five days ago where live poultry was sold, but the patient had no direct contact with the poultry.
The above comments from the March 17 CHP update describe the most recent H7N9 bird flu case imported to Hong Kong from Guangdong Province. The stable condition or the 5 month old infant was also noted in an update from the Guangdong Health and Family Planning website, as well as today’s WHO H7N9 update.
However, prior to the WHO update the CHP released a full set of sequences, A/Hong Kong/8113530/2014 (at GISAID), from the patient’s clinical sample. The CHP is to be commended for the rapid release of these important sequences.
Although the H7 sequence included the mammalian adaptation Q226L, the PB2 sequence, which usually has the mammalian adaptation E627K when isolated from severe case, had the avian amino acid glutamic acid at position 627. Moreover, the PA gene was most closely related PA sequences seen from northern China and did not have the mammalian adaptation L336M, which was becoming increasingly common in human cases in southern China.
The absence of these adaption raise concerns that milder H7N9 without these adaptation may be widespread, and largely missed due to surveillance efforts focused on more severe cases. This patient drew attention because she was arrived from Guangdong Province and had previously visited a live market. The PA sequence was most closely related to avian and human sequences from northern China, but the sequence was not closely related to any PA sequence at GISAID, once again signaling surveillance concerns.
These concerns have also been increased by the limited number of released sequences. The dearth of fall or winter H7N9 sequences from northern China as well as limited sequences from Guangdong, raises concerns that the large number geographic and familial cluster signal human to human transmission. The most recent WER included a phylogenetic tree of 2014 H7 sequences, which included multiple examples and clusters of identical sequences which have not been made public.
The withholding of these sequences, as well as the relationships between the associated cases, continues to raise pandemic concerns.