#13,905
One of the remarkable, and most worrying, things about influenza is its ability to continually re-invent itself, either via a slow process of antigenic drift, or rapidly through antigenic shift (reassortment).
- Antigenic drift causes small, incremental changes in the virus over time. Drift is the standard evolutionary process of influenza viruses, and often come about due to replication errors that are common with single-strand RNA viruses (see NIAID Video: Antigenic Drift).
- Shift occurs when one virus swap out chunks of their genetic code with gene segments from another virus. This is known as reassortment. While far less common than drift, shift can produce abrupt, dramatic, and sometimes pandemic inducing changes to the virus (see NIAID Video: How Influenza Pandemics Occur).
Yesterday Egypt's Ministry of Agriculture posted a short statement (see below) announcing the detection of a new (presumably HPAI) H5N2 virus on a local duck farm.
Details in this announcement are scant, and no OIE notification has yet appeared on the OIE Alerts site.
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| Screen Shot From Egyptian MOA Website |
We get a few additional details from local media, which were gleaned from a phone interview provided by Egypt's Deputy Minister of Agriculture (bolding mine). After which, I'll return with more.
(Continue . . . )Agriculture "announces the discovery of a new strain of bird flu h5n2
Raised Dr. Mona Mehrez Deputy Minister of Agriculture for animal husbandry and fishery and poultry, a detailed report to Dr. Izz al- Din Abu State Minister of Agriculture and Land Reclamation, about the discovery of a new disease of avian influenza and procedures for tackling the disease, particularly the discovery of the disease came to the efforts carried out by the General Authority for Veterinary Services on active investigation and the withdrawal of samples from poultry and duck farms.
Said Dr. Mona Mehrez Deputy Minister of Agriculture for animal husbandry and fishery resources, the discovery of a new type of bird flu "h5n2" as a result of the mixing of two viruses has resulted in a third virus, it was discovered in one of "ducks" farms which do not apply bio - safety, indicating that it was taking all preventive measures, dealing with the new strain type.
Said Dr. Mona Mehrez Deputy Minister of Agriculture, that all vaccines are available for the new type of bird flu, pointing out that the strain h5n1 "" of bird flu has not mutated, but the back strain of bird flu h5n2 "", and that the cases that have emerged in a duck farmer and not in poultry farms.
Although we don't tend to get as much information out of Egypt as we did a few years ago, we know there are three types of avian influenza that have taken up residence in Egypt since 2006.
From these three viruses alone there are enough genetic building blocks to come up with a new reassorted H5N2 virus in a couple of ways, and if additional (possibly local LPAI) viruses are involved, the number of possible permutations would increase even more.
- HPAI H5N1 which arrived in 2005
- LPAI H9N2 which was first reported in 2010
- HPAI H5N8 which arrived in late 2016
The short history of clade 2.3.4.4. H5 viruses - particularly HPAI H5N8 - has been one of continual evolution, frequent successful reassortment (into H5N6, H5N2, H5N5, etc.), and rapid geographic expansion - primarily via wild and migratory birds.
These viruses have sparked the largest avian epizootics on record in both Europe and North America, and have extended their reach all the way into the Southern Hemisphere.In December of 2017, and again last August, Russia - which had been plagued by scores of H5N8 outbreaks for more than a year - reported outbreaks of HPAI H5N2 in poultry farms in Kostroma Oblast.
The OIE confirmed last summer that the second virus was of clade 2.3.4.4. - which suggested it was a relatively new reassortment - likely from either HPAI H5N8 or HPAI H5N6.It is therefore possible that Egypt's `new' reassorted H5N2 is the product of HPAI H5N8 and either LPAI H9N2 (another highly promiscuous virus), or another local LPAI avian virus.
Another possibility - which we very recently discussed in J. Virology: Genetic Compatibility of Reassortants Between Avian H5N1 & H9N2 Influenza Viruses - is a reassortment arising from endemic H5N1 & H9N2.
That study warned:
In conclusion, our analyses indicated a substantial emergence potential of influenza virus reassortants derived from the H5N1 and H9N2 viruses currently cocirculating in Egypt, as well as the possibility of their high public health risk for humans relative to the parental H5N1 and H9N2 viruses. Cocirculation of the two influenza virus subtypes in birds may accelerate the emergence of novel viruses that may be a public health risk.
While the behavior - and possible threat to human health - from either reassortment would be hard to predict, both H5N1 and H9N2 have infected humans, while H5N8 has not.
An H5N1/H9N2 reassortment therefore would - at first glance, at least - appear to be the more worrisome of the two.Hopefully we'll get some more details on the pedigree of this new reassortment sooner rather than later. And while this will hopefully turn out to be nothing more than a one-off, localized event, the northbound spring migration has already begun, and that could potentially spread any new virus.
Meaning we need to be alert for any signs of HPAI along the migratory flyways in the months ahead as billions of birds to head to their high latitude roosting areas for the summer.
