#14,309
Influenza viruses are constantly reinventing themselves via two well established routes; Antigenic drift & 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).
In early 2015 Taiwan - along with Japan, the United States, Canada, and parts of Europe - was visited by a particularly robust, relatively new clade (2.3.4.4) of the H5 virus (see Taiwan Reports H5N8 On Goose Farm and `New Strain’ Of H5N2), which rapidly became endemic on the island nation.
Clade 2.3.4.4 H5 viruses are notorious for their ability to reassort and reinvent themselves into new subtypes (including H5N1, H5N2, H5N5, H5N6, H5N8, and H5N9).While Taiwan has had to contend primarily with H5N2 and H5N8, today we learn that - for the first time - they have detected an H5N5 virus. Its origins are still under investigation, so we don't know if this is a local reassortment, an imported virus, or (less likely) the product of an LPAI-to-HPAI mutation.
First the (translated) announcement from Taiwan's APHIS, then I'll return with a bit more.
The first time the detection of highly pathogenic H5N5 avian influenza virus, initially determined that the virus has not spread, called on the industry with epidemic control measures
Ref: 8376
Release date: 108-09-16
Published Authority: Animal and Plant Health Inspection Service
Council of Agriculture (COA) today (16 May) confirmed that the publication of the 12th District, Kaohsiung Qishan 1 duck (active surveillance) H5 subtype highly pathogenic bird flu cases, the animal health tests (livestock Wei ) further testing analysis, diagnosed as infected with H5N5 highly pathogenic avian influenza (HPAI) virus, the virus detected in 15 cases in wild birds in Europe between 2016 to 2018, and in Germany (3 turkey farm) and 克罗埃西亚 (4 poultry farm) poultry farm sporadic cases, the rest of the world around no serious epidemic.
Because for the first time detected cases of H5N5 bird flu virus, the COA can not be taken lightly, for the case of field three kilometers surrounding poultry farms have completed a comprehensive sampling and monitoring and found no new cases, initially determined that the virus has not spread .
COA pointed out that from Kaohsiung H5N5 bird flu cases, non-communicable diseases common to humans and animals, was the alternate on the eve of the season will start to strengthen surveillance for avian influenza among ducks reared high volume counties, subject to the further testing by animal health, 13 on the afternoon diagnosed with H5N5 subtype of HPAI, livestock guardian of the virus nucleic acid analysis, the H5 virus carrying the gene and 104 domestic invasion of H5 avian influenza virus most closely, N5 gene similar to the virus found in wild birds in Eurasia.
The source speculated that the presence of this virus strain H5N2 virus in Taiwan at this stage with wild birds carrying the virus HXN5 recombination, but it can not be completely ruled out by the wild birds come to carry. In addition, according to the World Organization for Animal Health (OIE) Terrestrial Animal manual review of the virus HA cleavage site amino acid sequence should be judged highly pathogenic avian influenza virus.
Kaohsiung City Animal Protection in post-informed of the outcome, then close links with the Council of Agriculture decided within 3 km radius around the poultry farms to conduct a comprehensive sample testing, and on the 15th to complete sampling for examination, specimen examined by animal health were negative, initially identified HPAI virus subtype H5N5 has not spread.
COA explanation, Taiwan to (107) of avian flu to H5N2 subtype of HPAI based, a total of 98 poultry farms occur; this (108) As of Year ended September 15, HPAI subtype H5N2 epidemic is still mainly , 55 poultry farms field occurs mainly infects birds land, the epidemic situation to last year although the decrease compared to the number of games, but still can not be taken lightly.
COA pointed out that currently only 1 domestic poultry farms confirmed H5N5 subtype of HPAI, is effective in preventing the spread of pathogens, will strengthen monitoring of the hot zone poultry farms, and the implementation of field area clean and disinfect the poultry industry through each group counseling industry, in addition to raising appeal again be sure to strengthen the poultry industry's anti-bird birdhouse facilities, poultry and avoid waiting (wild) birds in contact, while the implementation of access control, time out poultry farms, all personnel must replace clothing and shoes, and all kinds of vehicles, cages, equipment and other out, have to go through Chedi disinfection, quarantine function to enhance the venue of independent, effectively prevent the spread of avian influenza through various media, and new viruses and reduce the risk of spread. In addition, household poultry should also be observed daily independent poultry health situation, if there is an abnormal death warning, shall immediately notify the local animal epidemic prevention agencies, should not be thrown away sick or dead poultry, and with the necessary sampling and monitoring work, to serve Central Lee timely disposal of the local epidemic prevention authorities, together Fangdu spread of the epidemic, in violation of the relevant provisions will be notified and keeping heavy penalties, to ensure the safety of poultry industry and sustainable development.
The first time the detection of highly pathogenic H5N5 avian influenza virus, initially determined that the virus has not spread, called on the industry with epidemic control measures
Ref: 8376
Release date: 108-09-16
Published Authority: Animal and Plant Health Inspection Service
During Europe's 2016-2017 avian H5N8 epizootic, we saw a handful of `spinoff' reassortants, including HPAI H5N5, isolated from a duck collected in the Netherlands (see OIE Notification).
Germany's Friedrich-Loeffler-Institut (FLI) described this new virus as:
Since mid-December 2016 a further subtype, H5N5, has been circulating in wild birds, which now has first been introduced into a poultry holding. This virus is is likely to be a reassortant based on the original H5N8. Mixed viruses, so-called reassortants, of avian influenza viruses are generated, if several virus subtypes are present in one infected animal and exchange genetic material during replication. Generation of reassortants must be expected when different high and low pathogenic influenza viruses are circulating in one population.H5N5 appeared to fizzle after the spring of 2017, but another reassortment - H5N6 - returned the following year, showing up in both Asia and Europe.
Hopefully we'll get more detailed information about the clade (likely 2.3.4.4., but that needs to be confirmed) - and possible origins of this virus - in the days to come.In the meantime, this reminds us how quickly the existing fluscape can change, and why we need to be prepared for surprises.
