# 6364
Today Hong Kong’s CHP (Centre for Health Protection) released new details on their imported H5N1 case from neighboring Guangdong Province.
The virus has been identified as clade 2.3.2.1 – which you may recall was the subject of a press release from the FAO last August (see Bird Flu rears its head again) due to its ability to evade the current H5 poultry vaccines in use across much of Asia.
Because we’ve not discussed this clade in a while, a bit of a review, then today’s statement from the CHP.
While not new, clade 2.3.2.1 has been making inroads across much of Asia in recent years. You can see an overview of the evolution of the H5N1 virus since it emerged in 1996 in the graphic below.
H5N1, like all influenza A viruses, is constantly under pressure to change and mutate, looking for a biological advantage. Most of these mutations, thankfully, are evolutionary dead ends and fail to spread and thrive.
But in this viral version of king-of-the-hill, nature occasionally produces a more `fit’ and competitive virus, and it begins to dominate and spread.
One of these `new’ clades seeing much success over the past few years has been 2.3.2. I wrote of the spread of this emerging clade last year in What Goes Around, Comes Around and EID Journal: H5N1 Branching Out).
In the spring of 2011 we began to see reports of poultry vaccine failures in Vietnam due to the spread of a mutated version this clade (further classified as clade 2.3.2.1).
The spread of the 2.3.2.1 clade of the virus was characterized last September (see WHO Report : Antigenic & Genetic Characteristics of H5N1 & H9N2 Viruses) as having appeared in wild birds and poultry in Bangladesh, China Hong Kong SAR, India, Japan, the Republic of Korea, Myanmar, and Vietnam.
While the press briefly had a field day over this new strain the CDC , the OIE, and the World Health Organization quickly reminded us that while the bird flu threat remains, there was no evidence at the time to suggest that this new strain is any more transmissible to – and among – humans than the earlier strains.
WHO Statement On New Bird Flu Clade
OIE Statement On H5N1 Clade 2.3.2.1
And while we’ve continued to see sporadic human infections with the H5N1 virus, they have not (as yet) escalated in frequency with the spread of this new clade.
H5N1 remains primarily a disease threat to birds, as it has not yet adapted sufficiently well to human physiology to spread efficiently from human-to-human.
The concern, of course, is that given enough time and opportunities . . . it might.
All of which brings us to today’s update from Hong Kong’s CPH on the toddler being treated at the Princess Margaret Hospital.
The Centre for Health Protection (CHP) of the Department of Health today (June 4) provided further updates on the Influenza A (H5N1) case involving a 2-year-old boy.
Further tests conducted by the Public Health Laboratory Services Branch of the CHP on the Influenza A virus isolate from the nasopharyngeal aspirate taken from the boy showed that the H5 gene of the isolate belonged to clade 2.3.2.1, which is the same clade as the isolates from wild birds detected in 2011 and 2012 and in the imported human infection case in late 2010. So far all the genes characterised belong to avian origin and there is no evidence of resistance to the antiviral agent oseltamivir (Tamiflu).
The boy is currently receiving intensive care in the Paediatric Intensive Care Unit of Princess Margaret Hospital. Investigation into the cause of his obstructive hydrocephalus is still under way. His current condition remains serious.
The CHP so far has kept some 80 contacts under medical surveillance.
Nasopharyngeal aspirates taken from the parents and the five contacts who reported respiratory symptoms tested negative for Influenza A (H5).
As at 5pm today, a total of 20 public enquiries have been received on the DH hotline (2125 1111).
The investigation is continuing.Ends/Monday, June 4, 2012
Issued at HKT 17:54
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