Experts say the H5N1 bird flu virus’s risk to humans is low, but fear an impeding decimation of seal populations after tens of thousands of deaths in South America and Antarctica
Get our breaking news email, free app or daily news podcast
In 1996, geese in poultry farms in the Guangdong province of southern China started to get sick with a virus causing “bleeding and neurological dysfunction” and then death.
A strain of avian influenza had likely arrived as a relatively harmless virus in migrating wild birds but had morphed into something “highly pathogenic”, killing about 40% of infected geese.
Now, after appearing and disappearing, evolving and mutating and traversing the planet – leaving millions of dead birds and mammals in its wake – a descendant of that same H5N1 virus is, 30 years later, killing wild birds in Australia.
“Right from the beginning there was great concern about the emergence of this virus,” says Dr Frank Wong, a virologist and avian influenza expert at the CSIRO’s Australian Centre for Disease Preparedness.
Many avian influenza viruses are known as “low pathogenicity” because they cause only mild symptoms, or none at all. High pathogenicity viruses cause serious illnesses and death.
Avian influenza viruses are also classified by the two types of proteins on their surface – hemagglutinin that has 16 sub-types and neuraminidase, which has nine.
These are important because the proteins are what the virus uses to latch on to the cells of a host. The only versions of these avian viruses to have evolved into deadly strains are H5 and H7.
Wong says until 1996 a H5 virus had never been seen before spilling into domestic geese to then become highly pathogenetic in domestic birds.
“That was an immediate flag,” he says.
From the H5N1 virus detected in 1996, variants were seen in markets and farms in Hong Kong the next year.
In 2002, almost a million poultry birds in Hong Kong were culled after H5N1 detections.
“All the ducks and geese were free ranging and in the 1990s we get these outbreaks of HPAI (highly pathogenic avian influenza). This H5N1 Guangdong goose virus was isolated but they couldn’t control it,” says Prof Marcel Klaassen, a bird flu expert and ecologist at Deakin University who has been researching the H5N1 strain for 20 years.
“It circulated in Hong Kong and east Asia and it was not until 2005 that it was found in wildlife. By 2005, the virus has evolved into something that survives in some wild birds.
