Monday, February 06, 2023

Could Bird Flu become the next pandemic?

Bird Flu, or H5N1, has reportedly crossed into mammals both in the UK and in a number of places around the globe. But whilst some scientists have suggested it is not yet the time to panic, there is concern that the virus could pose a deadly risk to humans [BMJ].

On Thursday 2nd February 2023, the Animal and Plant Health Agency (APHA) confirmed that five foxes and four otters had tested positive for avian flu in England, Scotland and Wales since 2021 [Sky News / Guardian]. 

Around the globe the virus has also been found in dolphins, bears and cats. Meanwhile in Spain last year tests on a number of mink showed that they had been infected with H5N1 after they began dying at a farm in October [Science].

Avian influenza or "bird flu" has caused increased concerns across the world as experts prepare for the possible occurrence of the next human influenza pandemic. Previously, only influenza A has ever been shown to have the capacity to cause pandemics [CDC]. A/H5N1, a highly pathogenic avian influenza virus, is of particular concern [ECDC] . Outbreaks of this disease in birds, especially domestic poultry, have been detected across Southeast Asia at regular intervals since 2003, and have now affected parts of Africa and Europe.

Although it is by no means certain that HPAI [Highly Pathogenic Avian Influenza] A/H5N1 will be the source of the next pandemic, countries should be prepared for the inevitable occurrence of human pandemic influenza.

When mink at a farm in Galicia, a region in northwestern Spain, started to die in October 2022, veterinarians initially thought the culprit might be SARS-CoV-2, which has struck mink farms in several other countries. But lab tests soon revealed something scarier; the deadly avian influenza virus H5N1. Authorities immediately placed workers on the farm under quarantine restrictions. More than 50,000 mink at the facility were killed and their carcasses destroyed. Whilst none of the farm workers became infected the episode reignited long-smouldering fears that H5N1 could trigger a human pandemic.

Genetic sequencing showed the mink were infected with a new variant of H5N1 which included a genetic change that meant the animal-flu virus was better able to reproduce in mammals, according to a report by Nature [Eurosurveillance].

It is not clear how the mink contracted the virus given that there had been no H5N1 poultry outbreaks reported in the region. In the UK outbreaks in the fox and otter population have been put down to the animals scavenging habits and the possibility they ate infected birds or faeces.

There is "currently no reason to suspect that the jump is due to a change in the virus's genetic make-up", according to Dr Alastair Ward, associate professor of biodiversity and ecosystem management at the University of Leeds. He claims that foxes and otters, who are known to scavenge, likely ate bird carcasses which had high viral loads. "Such high exposure is likely to have overwhelmed the mammal's immune system, resulting in infection," he says.

Whilst it is rare for humans to contract bird flu, it has occurred on rare occasions, often where people have had close contact to infected birds for a significant period of time. Nonetheless some scientists fear that mutations could occur which might allow the virus to jump the species gap.

Global health officials are worried another strain could make a jump into humans, like H5N1 did in the late 1990s. It has since caused hundreds of human infections and deaths, but has not acquired the ability to transmit easily from person to person.

The greatest fear is that a deadly strain of avian flu could mutate into a pandemic form that can be passed easily between people - something that has not yet been seen [Reuters].

The Pirbright Institute, which carries out research into viral diseases in animals, warns that new avian flu virus strains are created frequently, meaning there is "a constant risk that one of the new strains may spread easily among people".

It is something that Michael Osterholm, author of the book The Deadliest Enemy, has long warned about.

In 2015 the WHO issued a document entitled "Warning Signals from the Volatile World of Influenza Viruses". In the report it warned of rapid changes in the development of potential human pandemic strains in birds.

Where humans have contracted Avian flu, the consequences can be deadly. Indeed it can have a high mortality rate as high as 50% [ECDC].

Alarm bells aren't ringing quite yet. Having shaken off the worst throws of the COVID-19 pandemic there are few that want to shout fire as the global economy picks itself up after the upheaval of lockdowns and economic turmoil.

The H5N1 virus is however causing massive damage to the poultry industry. It might only be a matter of time before it makes a jump and creates chaos in human society.

"Without a doubt, if you were to add up my entire public health career's concerns, worries, and—in some cases—nightmares, they collectively do not meet the concern, worry, and nightmares that I have about the issue of an impending pandemic of influenza," Osterholm said back in 2005 as he marked the inauguration of the Global Health Initiative [Wilson Center]. Less than 20 years on, his concerns remain.

The so-called "R naught" value, or the number of people infected by a single infected person, on average, for COVID initially ranged from 1.5 to 7, and now sits upwards of 12. The R naught value of H5N1 among birds is "around 100," according to Rajiv Chowdhury, senior epidemiologist and professor of global health at Florida International University. "The world is facing an unprecedented pandemic of avian flu among caged and wild bird populations."

Chowdhury and Osterholm are equally concerned about additional spread from birds to humans, and about possible transmission from humans who contract the bird flu to other humans, especially as the virus traverses the globe and makes the leap to more mammals, due to mutations [Fortune].

Osterholm has also raised his concerns about scientific research into influenza viruses, including H5N1, particularly so-called 'Gain of Function' experiments. Supporters of such studies say knowing which mutations help the virus spread in humans is useful for surveillance efforts and developing pandemic vaccines. However, GoF experiments have become the focus of attention since SARS-CoV-2 emerged with some believing that gain of function research at the Wuhan Institute of Virology spawned the virus that caused the COVID-19 pandemic.

While viruses can mutate naturally and jump species gaps without human intervention, safety lapses in federal labs with smallpox, anthrax, and avian influenza in 2014 offered a stark reminder of the "fallibility" of even the most secure labs [NBC / Science]. Should GoF experiments create highly contagious versions of H5N1 capable of human to human transmission, a leak could be devastating [Science].

It is conjecture that COVID-19 was the result of a lab-leak following GoF experiments on bat coronaviruses. It is also impossible to predict there won't be a leak from a Western laboratory carrying out similar experiments on H5N1 or other influenza viruses. It is equally impossible to say whether Avian flu will naturally mutate into a form capable of human to human transmission.

But the warnings are there for anyone willing to see. As Osterholm said in his 2017 book The Deadliest Enemy, "We can never be sure how close we are to the next mutation or evolutionary pressure that will lead us to the next pandemic."

tvnewswatch, London, UK