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Medical virologist and infectious diseases physician at NSW Health Pathology, Dr Jen Kok, discusses the worldwide bird flu outbreak and what we’re doing to prepare.
Avian influenza, commonly known as bird flu, is a viral disease of birds and is found around the world. Some strains have very minor effects on wild birds, while others can cause severe disease. Certain strains can infect mammals including seals, livestock, and occasionally humans.
The most well-known strains of bird flu are H5N1 and H7N9 and both have caused serious infections and deaths in humans.
A variant of H5N1, named clade 2.3.4.4b, causes significant illness and deaths in poultry, wild birds and mammals. It has spread rapidly across all continents except Australia and killed millions of wild birds. Human infections are rare and typically occur after close contact with sick birds and livestock.
The mortality rate of H5N1 in humans is about 50% in the almost 900 cases of people infected worldwide since 2003, but the mortality of the 2.3.4.4b clade is substantially lower.
We asked Dr Jen Kok, Medical Virologist and Director of the Centre for Infectious Diseases and Microbiology – Public Health (CIDM-PH) at the Institute of Clinical Pathology and Medical Research (ICPMR) to explain what is happening and how Australia is preparing.
“Ongoing surveillance to monitor for this variant is critical, particularly in the animal sector,” he said.
“But there is no need for panic. I would say we are alert, but not alarmed.”
Health authorities in Victoria and NSW have this year been working to contain outbreaks of different strains of bird flu on several poultry farms near Melbourne and Sydney.
Earlier this year the NSW Government launched its emergency biosecurity incident plan to manage the outbreaks.
Thousands of chickens have been euthanised and quarantine zones have been set up to restrict the movement of birds and equipment.
“The chickens culled on farms in Victoria have had H7N3 and H7N9 strains of avian influenza, and in NSW it’s the H7N8 strain, not the 2.3.4.4b variant causing concern elsewhere in the world,” Dr Kok said.
“The virus doesn’t typically infect humans, because they don’t have the receptors in their throats, noses or upper respiratory tracts that are susceptible to the current bird flu strain.”
Symptoms can be mild
Dr Kok points out that avian influenza doesn’t always present as just a respiratory illness.
“In overseas cases, one of the symptoms reported was conjunctivitis, which is a feature that we see with low pathogen avian influenza viruses.
“Some infected people just get red eyes and nothing else, some of them just have very mild symptoms.
“The under-recognition of mild symptoms may be skewing the high mortality rates that are reported. The mortality rate may be even lower because we don’t recognise as many mild cases or asymptomatic cases.”
Are we prepared for avian flu?
Dr Kok said Australia is well prepared for bird flu.
“This is not like COVID, it’s not a new virus. We know how it behaves and we know how to respond,” he said.
“NSW is prepared for diagnostic testing. The laboratory responses, the clinical responses, these are all essentially ready to go. As soon as the switch is flicked, all these plans should kick into place.”
He said in addition to monitoring animals, surveillance has also been ramped up to identify patients who are unwell with influenza.
“Those who are critically ill, those who’ve returned from overseas, those who have had contact with birds or sick animals, they’re at potentially increased risk of having avian flu,” Dr Kok said.
“So, if they have influenza A diagnosed, then they should have those viruses subtyped quickly to be able to say whether they have H5N1.
“Here at NSW Health Pathology in Westmead, we have the capacity to subtype viruses quickly, and we’re one of three World Health Organization (WHO) National Influenza Centres in the country able to do this work, the others are in Perth and Melbourne.”