An unprecedented monster is the bird flu that is currently sweeping the world. But where does flu number A/H5N1 actually come from? And what is the danger that it spreads to humans? A short guide, in five questions.
1| What is bird flu?
Take a hair, and imagine: balls that are a thousand times thinner. Those are the causes of bird flu. Influenza viruses, tiny packets of genetic material with only one mission: to penetrate cells and multiply, secretly piggybacking on the cell’s copying machine.
There are different types of flu virus, classified according to the studs on their outside. The influenza virus that currently lives in birds comes from group A, has type number 5 of the attachment protein ‘hemagglutinin’, and type number 1 of the protein ‘neuraminidase’, with which the virus cuts itself free from the host cell. Hence A/H5N1.
But that’s the molecular tinkering, birds breathing in the particles (via bird droppings or snot) have no idea. They become terribly ill if the virus mainly attacks their respiratory tract and brain. The animal sniffles, develops a swollen head and eyelids, becomes disoriented, and dies—some species more often than others, for reasons scientists don’t quite understand.
2| Where does H5N1 come from?
Until the mid-1990s, bird flu was fairly harmless. Outbreaks of H5 and H7 viruses did occur, but were fairly manageable. And roaming among wild birds hardly did the bird flu.
But that was before the current H5N1 flu appeared in 1996, on a goose farm in China. Gradually, the virus began to spread, first over China, and from 2003 onwards into Asia and Africa. From 2005, migrating waterfowl carried the virus to Europe. A sign that the virus had ‘completely changed’, writes professor of veterinary medicine Arjan Stegeman (Utrecht University) in a review article. “A virus strictly associated with poultry had adapted to wild waterfowl.”
In 2014, H5N1 took the next step. A new, super-contagious variant, designated 2.3.4.4, took hold. Since then the end has been lost. The virus is active in dozens of countries, and because it nested in wild birds and birds that are in our country all year round, H5N1 was also present in summer for the first time this year. The virus has now also reached the sea: H5N1 caused devastating outbreaks in gulls, terns and gannets, among others.
‘All seabird ecologists have been taken by surprise,’ says marine ecologist Kees Camphuysen of the Netherlands Institute for Sea Research (Nioz). “The mortality we are seeing is absolutely unprecedented. Sometimes more than 70 or 80 percent of a population dies in a few months.’
With the conquest of the oceans, the advance of H5N1 worldwide seems to have become unstoppable, Camphuysen thinks. At the end of September, the virus even appeared to spread to penguins in the tip of South Africa.
3| What is the risk that the Netherlands will become the new Wuhan?
No, you don’t want a pandemic with this virus. Of the 880 people the WHO knows were once infected with an H5N1 virus after close contact with infected birds, 450 died. Half! The good news is that in the West, only two people are known to have infected the virus, a British and an American, who both survived.
And those are the individual cases. The nightmare scenario is that, for example, a bird flu virus infects someone with a malfunctioning immune system, uses that person as a ‘breeding vessel’ to adapt to humans – and then causes a worldwide flu pandemic. This does not only apply to H5N1: virologists also have restless nights because of the Asian bird flu viruses H3N8, H5N6 and H7N9.
One consolation: so far, only H1, H2, and H3 viruses fit on human cells. Moreover, the earlier flu viruses that spread to humans often first passed around pigs as an ‘intermediate station’, where they become more accustomed to a mammalian body.
But it remains a game of chance. In May, German virologists discovered that the infamous 1918 Spanish Flu H1N1, responsible for 50 to perhaps 100 million deaths, probably really jumped directly from birds to humans.
4| Is it bad to eat contaminated meat?
Although infections on humans are rare, they do occur. Usually by being around infected animals, and thus breathing in the virus, through dust particles or droplets released when an infected bird flutters, shakes or scratches itself. By the way, touch is also possible if you get the virus on your hands and get it on your eyes, mouth or nose.
Hence the advice: avoid contact with sick or dead animals, explains veterinary microbiologist Evelien Germeraad of Wageningen University by email. The chance of contamination via eggs or chicken meat, if properly prepared, is negligible. ‘The bird flu virus is sporadically found in mammals that have eaten birds infected with bird flu. Such transmission has not been demonstrated in humans.’
That wisdom is not entirely carved out of stone, by the way. The WHO knows of a few cases where the virus appears to have infected someone through raw blood. Take the 27-year-old Chinese woman who died of bird flu in early 2009: she had been exposed to fresh duck blood and raw chicken hearts, in front of her husband’s food stall.
About the same goes for eggs. Raw eggs could theoretically contain virus, according to an analysis by US government researchers published this year. But it is unproven that a human was ever infected by an egg, and after cooking or baking the virus is harmless anyway.
5| What can we expect from a vaccine?
In Lelystad, three vaccines against H5N1, which would one day be automatically injected into the egg, are being investigated: a French protein vaccine already authorized in various countries, a newly developed DNA vaccine made in Belgium and a third vaccine about which no announcement has been made. Such an envisaged vaccine should ‘provide good protection against disease, but also against the spread of the virus’, says Wageningen University in a press release.
But whether that is a feasible card is the question. Take the French vaccine. It protects about 80 to 100 percent against mortality, according to results of earlier chicken trials, but the vaccine often only worked by a few tens of percent against disease and transmission of the virus. A recent trial with the Belgian vaccine, meanwhile, indicated that different chicken breeds react very differently to the jab.