In the last year or so, virologists have been watching a deadly pandemic spread around the world, killing tens of millions. No, it’s not Covid-19. And yes, I’m deadly serious.
It’s not killing humans though (not now anyway) but birds. It’s in fact a panzootic, as an animal pandemic is called. Bird flu, or more precisely, highly pathogenic avian influenza, is to blame. So why are virologists on alert? I’ll explain later, but first, here’s how devastating this disease is for birds.
Wild birds have been literally dropping dead, dying in droves in their colonies. Some islands off the coast of Scotland where migratory birds flock have been closed to the public as they were covered with the carcasses of birds. In the coastal areas of Peru, over 60,000 dead birds have been found dead, including endangered species such as pelicans, boobies, and cormorants. Conservationists fear some seabird species could become extinct.
This strain of avian flu is one of the most infectious diseases known: just a teaspoon of infected bird faeces (that can spread by wind with a viral load that can survive for six weeks) can kill a shedload of poultry. Thus the poultry “lockdowns”, with farmers keeping birds inside.
If one bird falls ill, the entire flock must be culled. In Europe, 50 million chickens have been culled; in the United States, it’s even more. In Japan, many prefectures are struggling to find land to bury the 17 million chickens culled, broadcaster NHK reported recently. Such huge losses have led to chicken and egg shortages and price hikes in some countries.
Malaysia has not faced such outbreaks, fortunately. But the virus, the influenza subtype H5N1, is spreading globally – and even among wild mammals such as seals, otters, foxes, bears, raccoon dogs, and cats, which apparently had contact with infected birds.
The big question is, what about humans? Since H5N1 was first found in China in 1996, infection among humans has been rare but often severe: of the several hundred humans infected, half died. Importantly, the likelihood of human-to-human transmission – the real worry – remains low, based on virological evidence, says the World Health Organization (WHO).
In February, there was a scare when an 11-year-old girl died of H5N1 in a village in Cambodia. Health workers immediately descended on the village, isolated the girl’s close contacts, and tested dozens of people. Her father tested positive for H5N1, but reassuringly, no one else did, and no human-to-human spread occurred, experts say. The girl and her father apparently had direct contact with dead birds.
Cambodia shared the sequencing of the virus, which showed that this was an older clade of H5N1 (2.3.2.1c), different from the deadly H5N1 clade (2.3.4.4b) now circulating and devastating birds, WHO reported.
That latter clade has infected only a handful of humans. But one outbreak on a Spanish mink farm has alarmed scientists because thousands of minks died, pen by pen, suggesting mammal-to-mammal spread. Tests confirmed a mutation in the virus. The minks were all culled, their carcasses destroyed, and farm workers were placed under quarantine.
The several hundred sea lions in Peru dying recently of H5N1 have also raised concerns. Some scientists question the theory that all the sea lions ate infected birds.
Experts still believe the risk of H5N1 is low, but are on alert. The chance of a more dangerous mutation occurring does increase with so much virus circulating, and among so many different species. The 30 billion farmed chickens globally also provide more opportunity for viral spread.
Viruses jumping species to spread in a new host is how many deadly epidemics and pandemics among humans begin. The new host will have no previous immunity, so the virus is more dangerous.
Most scientists believe Covid-19 began this way. The 2003 SARS (severe acute respiratory syndrome) coronavirus jumped from bats to civets sold in a market to humans. HIV and monkeypox spread from monkeys; Ebola from bats; plague from rats; and the Nipah virus went from fruit bats to pigs to humans here in Malaysia in 1998-1999.
Bats are reservoir hosts of various viruses, and wild aquatic birds of avian flu. The danger arises when new strains mutate to spread among humans. That’s what happened in the worst pandemic in modern history, the 1918 influenza pandemic which killed as many as 50 million people; it was caused by avian flu, H1N1.
The 1957 “Asian flu”, first reported in Singapore, and 1968’s “Hong Kong flu”, which killed at least a million people each, were originally avian flu viruses too.
It is precisely because of such events that new influenza viruses have been monitored for decades. Experts have long been preparing for a flu pandemic (rather than a coronavirus pandemic) – it’s a question of when, as WHO says. When Covid-19 emerged, many countries relied on their influenza surveillance systems and laboratories to monitor the new virus.
The good news is that countries now have better surveillance systems and laboratories – genetic sequencing has proliferated due to Covid-19. And as the Cambodia case showed, rapid responses teams can act quickly even in resource-limited countries.
But as this bird flu outbreak shows, nature will always have the upper hand. We shouldn’t forget that.
Human Writes columnist Mangai Balasegaram writes mostly on health but also delves into anything on being human. She has worked with international public health bodies and has a Masters in public health. Write to her at lifestyle@thestar.com.my. The views expressed here are entirely the writer's own.
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