Bird flu on the beach
The current outbreak of H5N1 avian influenza is the biggest on record. But as the virus spreads from wild birds to mink and other mammals, how worried should we be?
The other week, my wife, daughter, and I were strolling along Covehithe, a glorious stretch of beach in east Suffolk, when we spotted two brown hulks buried in the sand. From a distance, they looked like the remains of trees that had once commanded views from the nearby clifftops, until, battered by the winds, the land had given way and they had fallen from their perches.
But as we drew closer, our dog – a large, white Goldendoodle - caught the scent of something rotting and bolted. The next thing we knew he was rolling ecstatically on one of the hulks, covering himself in sand and what we soon realised were tiny flecks of blood.
It is not unusual to see seals wash up at Covehithe but two struck us as peculiar and, concerned that our dog may have been contaminated with whatever had done for them, we coaxed him into the surf. It was only when we were satisfied he was clean and no longer posed a risk to himself or us, that we spotted a dead seagull close by.
I have no reason to believe that the dead seals, or seagull, had been infected with H5N1, the highly pathogenic avian influenza virus that is object of growing international alarm, but I could not help but see them as omens.
Since October 2021, when the latest strain of the virus – known as H5N1 2.3.4.4b – began spreading worldwide, some 140 million poultry, including 60 million in North America and 48 million in Europe, have been killed by either disease or culling, according to the World Organization for Animal Health. That makes the current outbreak the biggest on record.
Suffolk and Norfolk are particular hotbeds of infection, with a map of the region dotted with blue and yellow protection zones and poultry farmers under strict instructions to cover their chicken runs with netting to prevent their flocks being infected by wild geese and other migratory birds, who transmit the virus year-round.
The good news, so far, is that there have been just 300 confirmed cases in English birds and only one person – a retired engineer living in Devon – is known to have contracted the virus (he most likely caught H5N1 from some ducks which lived inside his home). But following the announcement last week that an 11-year-old Cambodian girl had died of H5N1 following an outbreak in ducks and chickens in a village 60 miles southeast of the Cambodian capital Phnom Penh, the World Health Organization is on high alert.
The problem is that although H5N1 has been circulating for years, few people have any immunity to the virus, meaning that, like SARS-CoV-2 – the coronavirus that emerged unexpectedly in China in 2019, sparking the pandemic of Covid-19 - it has the potential to become a pandemic at any time.
In order to do so, however, it would probably first need to passage through another mammalian host, such as a pig or a seal. So far, there is no evidence of that having occurred in Suffolk but H5N1 has already been detected in harbour and grey seals in Scotland, and last month El Pais reported that marine biologists in Peru had discovered 100 dead sea lions floating in the waters off Isla Asia, less than 60 miles south of the capital Lima.
Before dying, the animals – majestic carnivores that can weigh up to 350 kilos – were observed suffering from agonising convulsions and struggling to swim. In the last two years, other species of mammal have also been infected, including otters, foxes and minks, which share many of the same respiratory receptors as humans and are known to be susceptible to both human influenzas and Covid-19.
So, how worried should we be? And what is it like to be infected with H5N1?
Eighteen years ago, during the outbreak that swept Southeast Asia in 2005, I travelled to Hanoi, in Vietnam, to speak to a man who had been hospitalized with the virus and had lived to tell the tale. With the help of a local photographer, I tracked Nguyen Thanh Hung down to a tiny apartment in a backstreet of Hanoi.
A wiry cement salesman with a passion for long-distance running, Hung, who was then 42, had fallen ill after nursing his sick brother in hospital. Hung’s ordeal began when he’d attended the funeral of his brother’s son the previous December. The funeral coincided with Tet – Vietnam’s version of Thanksgiving – and after the service Hung and his brother had sat down to a meal of duck’s blood soup, a local delicacy. Hung hardly touched the soup, which is made from raw, congealed duck’s blood. However, two days later his brother developed a headache and breathing difficulties and was taken to Hanoi’s tropical diseases hospital. Learning his brother was ill, Hung rushed to his bedside where he sat vigil for the next five days, watching as his brother’s breathing became steadily more laboured.
In a scene that would foreshadow the experiences of Covid-19 patients fifteen years later, Hung’s brother was intubated and placed on a respirator. But he found the procedure uncomfortable and was administered pressurized oxygen via a face mask instead. However, Hung told me, his brother kept on removing the mask, forcing Hung to lean across his body to replace it. “I was about 30cm from his face,” he told me.
Hung’s brother died on 9 January, prompting Hung to return to their village for a second funeral. Then, two days later, Hung also began to feel unwell. X-rays revealed an ominous white shadow on his lung. Initially, doctors suspected tuberculosis but when Hung’s temperature soared he was also taken to Hanoi’s tropical diseases hospital.
“My whole skull was throbbing,” he told me. “I felt like I was going colour blind and the walls were pressing in on me.”
Ten days later, a chronically backlogged lab sent back word that his brother had died of H5N1. Soon after, it was confirmed Hung had the virus, too.
“I was quite scared at first, but by then I was starting to feel better. The fever and pain were over and I thought to myself, ‘I'm through the worst’.” Nonetheless, it was another ten days before Hung was well enough to be discharged.
To this day, it is not known how Hung contracted the virus. Was it through imbibing the raw duck’s blood or was he infected at his brother’s bedside? The latter, of course, would be extremely worrying, suggesting that H5N1 can be transmitted as an aerosol from person to person. Although scientists took swabs from Hung in order to culture the virus and conduct more precise molecular studies, the tests were inconclusive. However, Peter Horby, then the WHO’s representative in Hanoi, now director of the Pandemic Sciences Institute at the University of Oxford, could not rule of the possibility of “human-to-human transmission”
If so, it would not be the only occasion. Similar “family clusters”, where two or more members of the same family have fallen ill with H5N1, have been recorded in Thailand, China, Pakistan and Hong Kong, and in 2006 Indonesia reported the largest cluster of H5N1 to date, when seven members of the same family contracted the virus. However, in no instance was there evidence the virus had been transmitted to the wider community, and in only one case of suspected human-to-human transmission, involving an 11-year old Thai girl, could researchers be confident that a relative who went on to develop the same illness had not been exposed to diseased poultry, making the girl the likely source.
In the case of the Cambodian girl who died of H5N1 last week, 12 people who had contact with her are now being investigated. The good news is that the virus belongs to a different clade than the one responsible for outbreaks in wild birds seen in other parts of the world and, so far, just one person – the girl’s father – has tested positive. Still, it is yet another reminder the threat has not gone away.
The worry is that the longer the current iteration of the virus circulates – and the more that wild birds transmit the virus to domestic poultry and back again – the more likely it is that it will pick up mutations that make it more transmissible to and between mammals. Such an event may already have occurred last October at a fur farm in northwest Spain where 52,000 American mink were infected with the virus.
As the virus spread from pen to pen, the mink stopped eating and began salivating excessively. Next, they started to experience tremors and developed bloody snouts. Most were dead within one to two days.
No one is certain how the virus got into the fur farm. It is possible the mink were fed contaminated poultry, but according to a report in the journal Eurosurveillance the more likely source was wild birds - the mink are housed in wire cages and partially open barns, making for easy egress.
Whatever the case, the onset was dramatic. Within weeks, there were multiple hotspots and by the end of October the whole complex was affected, suggesting, in the words of the Eurosurveillance report, that “onward transmission of the virus to other minks may have taken place”.
If that is the case – and it’s a big if – it would be incredibly concerning as it suggests that H5N1, which is usually communicated via contaminated blood and/or faecal matter, may be mutating so at to become an airborne pathogen. Indeed, mink are known to be susceptible to human respiratory diseases and during the pandemic of Covid-19 there were repeated outbreaks of SARS-Cov-2 on mink farms in the Netherlands. These outbreaks probably began when farm workers infected with SARS-CoV-2 sneezed on the mink but, in at least two cases, the mink also appear to have transmitted the virus back to farm hands.
However, perhaps the best evidence for H5N1’s pandemic potential comes from a controversial “gain-of-function” study conducted in 2011 at a laboratory the Netherlands. In that study, a team of researchers led by Ron Fouchier, succeeded in transforming H5N1 into an aerosol virus by repeatedly transmitting it between ferrets, a species closely related to mink.
As with the recent outbreak at the Spanish fur farm, the onset of illness was abrupt, with the ferrets suffering sudden loss of appetite, hypersalivation, bloody snouts and tremors. Although none of the ferrets died, and the virus transmitted poorly through the air, it took just five mutations to transform the H5N1 virus into an aerosol.
Not surprisingly, the study provoked hysterical headlines about a “doomsday virus” and prompted regulators to impose a moratorium on further experimentation (the moratorium was lifted in 2013).
In 2018, I interviewed Ron Fouchier for my podcast and discussed the implications of his experiment. You can listen to the interview here.
Fouchier has always maintained there was no risk of the ferret-induced virus escaping his laboratory at the Erasmus Centre in Rotterdam. However, other researchers disagreed, arguing that the Rotterdam facility fell short of the highest biosecurity standards.
Following the furore over similar gain-of-function studies involving SARS-like coronaviruses at the Wuhan Institute for Virology, in China, such studies remain highly controversial. But as the ongoing worldwide outbreaks of H5N1 in minks, seals and other mammals demonstrate, such experiments are happening in nature all the time.
The difference is that when they occur in nature, there is nothing to prevent the virus spilling over into human populations. All the more reason then, to avoid suspect carcasses that wash up on the beach.