Bird flu virus is back, should we be worried?

“We are seeing an unprecedented explosion in outbreaks of new bird flu viruses, which historically have presented the greatest pandemic risk and certainly have the potential to be worse than Covid,” says Dr Michael Greger, author of Bird Flu: A Virus of Our Own Hatching.

Avian flu is back. While it never really went away, this year we are seeing a resurgence in bird flu. Eight variants are currently in circulation, with some concern among experts that one of these could “jump” and cause an outbreak in humans.

Last week, avian influenza A (H5N1) was confirmed in a turkey flock in Co Monaghan, with a second outbreak in the county confirmed last Wednesday. The spread of highly pathogenic avian influenza, commonly called bird flu, has put the poultry industry on alert after previous outbreaks led to the culling of tens of thousands of birds. It comes on top of several outbreaks of severe bird flu in Europe and Asia in recent months – a clear sign the virus is spreading quickly again. China has reported 21 human infections with a different H5N6 subtype of avian influenza so far this year, more than in the whole of 2020.

The nightmare scenario is where both viruses successfully mix in humans and produce a virulent new strain of influenza and with it the likelihood of a new pandemic

Bird flu circulates naturally among wild birds, and when they migrate to Ireland in winter the disease can spread to poultry and other captive birds. And while most outbreaks do not affect humans, some have proven deadly in the past.

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Avian influenza is an infectious disease of birds caused by type A strains of the influenza virus. Influenza A is one of three types of flu virus. A and B have the greatest impact on human health, with influenza A the type responsible for previous epidemics and pandemics.

The influenza virus can change its characteristics with relative ease. Minor changes in the surface of the virus – involving proteins called haemagglutinin (H) and neuraminidase (N) – occur between each influenza season. Influenza A viruses have 16 H subtypes and 9 N subtypes, various combinations of which result in the naming system (for example H1N1 or H5N8). Minor changes are referred to as antigenic drift and are the reason why it is necessary to reformulate the flu vaccine annually.

When major alterations to the surface proteins occur, it is referred to as antigenic shift. A completely new virus then emerges, along with the likelihood of an influenza pandemic. Luckily, such major changes rarely occur.

The main human virus type in circulation so far this winter, albeit in small numbers, is influenza A (H3N2). In previous years when this type dominated, it targeted older people in particular. Flu virus invades the cells of the human body by injecting a spike of its own cell wall into the cells of the respiratory tract. It then begins to multiply, using the human cell as a new home.

The virus reaches the respiratory tract via droplets in the air, which come from the coughs and sneezes of other flu victims. Influenza reproduces rapidly in the throat and the lining of the lungs. From these initial sites in the respiratory tract it begins to invade the rest of the body by way of the bloodstream.

So with H1N1 avian flu identified among turkeys in Co Monaghan and H3N2 flu looking like it will be the main cause of influenza in humans, what are the chances of an epidemic hitting us over the coming months?

The nightmare scenario is that both viruses successfully mix in humans and produce a virulent new strain of influenza – and with it the likelihood of a new pandemic. An avian flu infecting someone who is also suffering from the human form of flu would create the ideal conditions for the avian flu to swap genes with the human flu, making it far more infectious – a “perfect storm” for a pandemic to commence.

Flu viruses have a high mutation rate and can exchange genes when two viruses simultaneously infect a single host. These genetic changes allow them to change their make-up and escape immunity in their host and continue spreading.

However, the Health Protection Surveillance Centre (HPSC) has said that no human infections with the latest avian flu have been reported in Europe, and therefore the risk to humans is considered very low. And the Department of Agriculture, Food and the Marine has said there is no evidence that the consumption of poultry meat or poultry meat products carries a risk of infection.

Are you putting yourself and your family at risk by having a turkey dinner this Christmas? There is no evidence that eating well-cooked turkey meat can give you avian flu

But we know bird flu can affect humans in rare cases if people touch infected birds, their droppings or bedding, or while preparing infected poultry for cooking. It has happened before, initially in Hong Kong in 1997 when an outbreak of highly pathogenic H5N1 viruses in poultry infected 18 people and caused 6 deaths.

This avian virus subsequently spread via migratory wildfowl to poultry in South East Asia, mutating as it travelled. By 2006, it had spread to Egypt, from where it travelled to Europe. More than 700 human infections with Asian H5N1 viruses have been reported to the World Health Organisation; in the majority of cases, people got the avian virus infection after direct or close contact with sick or dead poultry infected with the virus. Although rare, human infection with avian H5N1 carries a high mortality (in the region of 60 per cent).

How might a doctor know you have avian flu? Firstly, you will have typical flu symptoms: signs of acute respiratory infection (cough, sore throat and runny nose) with a temperature greater than 38 degrees Celsius. Muscle aches, headache and a general feeling of malaise are common. Diarrhoea and vomiting may also occur. Typically, the symptoms come on within hours, rather than the slower development of symptoms seen with the common cold.

In addition, the doctor will want to know if you have been either in contact with poultry or wild birds, or been within 1 metre of a person diagnosed with H5N1 influenza, or have worked in a laboratory where there is a potential exposure to the avian flu virus.

Treatment is with an oral anti-viral drug such as oseltamivir (Tamiflu). Anti-virals work by attacking the neuraminidase protein sitting on the surface of the virus. Neuraminidase enables the replicating influenza virus to break away from the cell it initially invaded and spread throughout the body.

Neuraminidase inhibitors prevent newly formed influenza particles from escaping infected cells, thereby interrupting the spread of infection within the body. To be effective, the drug must be started within 48 hours of the onset of flu symptoms.

Are you putting yourself and your family at risk by having a turkey dinner this Christmas? There is no evidence that eating well-cooked turkey meat can give you avian flu. However take care when preparing the turkey, keep surfaces spotlessly clean and carefully follow the Christmas dinner guidance issued by the all-island body Safefood (safefood.net).

Will there even be a turkey dinner if the avian flu spreads among Irish poultry over the coming weeks? While the Department of Agriculture will euthanise any flocks that become infected, their rigorous policy of placing protection and surveillance zones around any infected holding, along with other biosecurity measures, should prevent a substantial threat to turkey supply.

Avian influenza, alongside swine flu, has long been expected to be the trigger for the next global infectious disease pandemic. Its resurgence is a warning that a future Covid-19-like pandemic may occur sooner than those of us struggling through the current pandemic can even contemplate.

Avian Flu on the rise in 2021

January 15th-February 4th, 2021: 410 new avian influenza outbreaks in domestic birds (subtypes H5, H5N1, H5N5, and H5N8) and 233 new outbreaks in non-poultry (subtypes H5, H5N1, H5N3, H5N4, H5N5 and H5N8) were reported in Asia, Europe and Africa. "The number of new and ongoing outbreaks reported by countries, notably in Asia and Europe continue to be significant during this period." – World Organisation for Animal Health.

February 24th-May 14th, 2021: 1,672 highly pathogenic avian influenza virus detections were reported in 24 EU/EEA countries and the UK in poultry and wild birds. These figures represent "a large and devastating epidemic." – European Food Safety Authority.

May-September 2021: China's Centre for Disease Control (CDC) identified several mutations in recent H5N6 cases. The spread of the H5N6 virus is now a "serious threat" to the poultry industry and human health, said Gao Fu, CDC director.

In a surveillance report, The European Centre for Disease Control and Prevention (ECDC) said it had identified some 162 highly pathogenic avian influenza viruses in 17 EU/EEA countries and the UK. They were recorded in poultry (51), wild (91) and captive birds (20). The detections in poultry were mainly reported by Kosovo (20), Poland (17) and Albania (6). “The risk of infection for the general population in the EU/EEA is assessed as very low… with large uncertainty due to the high diversity of circulating viruses in the bird populations,” it said.

November 20th, 2021: The Department of Agriculture, Food and the Marine announce the Republic's first avian flu outbreak of 2021. Test results identified evidence of highly pathogenic avian influenza H5N1 in samples from a turkey flock in Co Monaghan. "[The virus] had already been confirmed in [individual] wild birds in a number of counties across the country in recent weeks," it added.

November 24th, 2021: A second outbreak of avian flu was detected in a chicken broiler farm in Co Monaghan.

Additional reporting – Guardian