again in Europe in 2021 and the current lineage of concern has swept across the continent<\/a>, through North and South America, to Antarctica and now Australia.<\/p>\nSince appearing in 1996, H5N1 viruses have infected more than 400 bird species and more than 100 mammal species, in particular seals and sea lions and also dairy cattle in the US.<\/p>\n
\u201cInfluenza viruses and how they impact different hosts is really a numbers game,\u201d Wong says.<\/p>\n
\u201cThe more types of host animals that it is allowed to infect without there being some control, the more chances it has to pick up new traits.<\/p>\n
\u201cIt\u2019s most successful trait is adaptability. So you want to give it as hard a time as you can to minimise its opportunity to become even more adapted to environments where you don\u2019t want it.\u201d<\/p>\n
Avian influenza viruses can evolve quickly because they are prone to errors when their genes are being continually copied.<\/p>\n
A southern giant petrel found at Knights Beach, Port Elliott, South Australia, that was later confirmed to have H5N1 bird flu. Photograph: Wildlife Welfare Org<\/p>\n
\u201cMost mutations are not successful but, given the right environment and situation, some mutations might give an advantage,\u201d Wong says.<\/p>\n
Farming poultry in dense populations for human consumption has helped new versions of the viruses to emerge.<\/p>\n
\u201cIn a way, it\u2019s like an incubator for highly pathogenic avian influenza that you don\u2019t see in the wild environment,\u201d Wong says.<\/p>\n
\u201cIn the wild it is not to the virus\u2019s benefit to kill its host. But in a domestic chicken flock, if a virus mutates from low pathogenicity to high, it selects for that trait because the infection burns through that population.\u201d<\/p>\n
Klaassen goes even further. \u201cThis is a man-made virus,\u201d he says. \u201cDid these viruses evolve in wildlife? No, they did not.<\/p>\n
\u201cLow pathogenic viruses come in and, with high densities of birds and large numbers, you have an ideal environment for a virus to evolve. All of the high pathogenicity influenza viruses evolve in poultry.\u201d<\/p>\n
Jump to mammals<\/p>\n
Since 1997, there have been about 500 human deaths from H5N1 \u2013 almost all of the cases recorded among people working in close quarters with infected poultry.<\/p>\n
Health authorities say the risk for humans is low, and there have been no recorded cases of human-to-human transmission of the virus.<\/p>\n
But H5N1 has infected mammal species \u2013 in particular, pinnipeds like seals and sea lions that tend to share the same spaces as infected wild waterbirds.<\/p>\n
\u201cAt one beach we saw a line of dead elephant seals \u2013 a whole tideline of dead animals,\u201d remembers Dr Rachael Gray, a veterinary scientist at the University of Sydney.<\/p>\n
Gray was monitoring for the disease in Antarctica in late 2023 \u2013 \u201cessentially picking up poo\u201d \u2013 when she witnessed the tide of death.<\/p>\n
\u201cIt was devastating,\u201d she says. \u201cIn birds you see respiratory symptoms \u2013 nasal discharges. But what we are seeing more of are these neurological signs. In pinnipeds, they can\u2019t walk properly. They have seizures and you see this clouding of their cornea. It is distressing to see.<\/p>\n
\u201cWhen it sweeps through a colony, you are talking two to four days [of symptoms before death] in birds and a little longer for mammals.<\/p>\n
\u201cThe virus has become well adapted at getting into mammal cells.\u201d<\/p>\n
Tens of thousands of pinnipeds have died of the virus in South America and Antarctica, and Gray holds grave fears for what could be in store for Australia\u2019s three resident pinnipeds \u2013 the New Zealand fur seal, the Australian fur seal and the endangered Australian sea lion<\/a>.<\/p>\nDr Rachael Gray has grave fears for the endangered Australian sea lion. Photograph: Brad Leue\/Alamy<\/p>\n
\u201cOn the first incursion, it will be awful,\u201d she says. \u201cSome might develop immunity, and hopefully that gets passed on to their offspring, but I don\u2019t think we know enough yet [on how the virus response will evolve].<\/p>\n
\u201cThe virus can survive for extended periods of time on different surfaces, particularly in cool conditions. That gives the virus a better chance to survive [in Australia] because it has arrived in our winter.\u201d<\/p>\n
H5N1 arrived in Australia in migratory seabirds from the sub-Antarctic and genetic testing of the birds showed the virus was the same type that had killed thousands of elephant seals pups at Heard Island.<\/p>\n
\u201cEvery year we got through without it we thought, \u2018maybe Australia\u2019s geographic isolation will help us\u2019,\u201d Gray says.<\/p>\n
\u201cBut that was a naive hope and now, maybe, I have naive hope that it won\u2019t hit our sea lions and fur seals. History is telling me the opposite.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"In 1996, geese in poultry farms in the Guangdong province of southern China started to get sick with…\n","protected":false},"author":2,"featured_media":568959,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[10],"tags":[134,111,139,69],"class_list":["post-568958","post","type-post","status-publish","format-standard","has-post-thumbnail","category-health","tag-health","tag-new-zealand","tag-newzealand","tag-nz"],"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/568958","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/comments?post=568958"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/posts\/568958\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media\/568959"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/media?parent=568958"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/categories?post=568958"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/nz\/wp-json\/wp\/v2\/tags?post=568958"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}