How to make sense of H10N8, H1N1, H7N9, and other bewildering bird flu names

H10N8 is the latest bird flu to come out of China and, potentially, decimate humanity like in that Gwyneth Paltrow movie. You may have previously been mortally frightened by news about H1N1, which killed up to 100 million people in 1918 and another 15,000 in 2009 and 2010. Or maybe you’ve been reading about H7N9, which has been connected to just about 100 human deaths and is the cause of a massive poultry cull in Hong Kong this week:

An health officer packs dead chickens at a wholesale poultry market in Hong Kong January 28, 2014. Hong Kong began culling 20,000 chickens and suspended imports of fresh poultry from mainland China for 21 days on Tuesday after the discovery of the H7N9 bird flu virus in a batch of live chicken from the southern province of Guangdong. REUTERS/Tyrone Siu (CHINA - Tags: ANIMALS ENVIRONMENT HEALTH SCIENCE TECHNOLOGY) - RTX17XS1
A health officer packs dead chickens at a wholesale poultry market in Hong Kong. (Reuters/Tyrone Siu)

Is H10N8 10 times more deadly than H1N1—or is it eight times, or 80? Not at all. The names refer to the two kinds of spiky protein that influenza A viruses wear on their surfaces, all the better to burrow into the hosts’ cells. H is for hemagglutinin and there are 16 varieties; N is for neuraminidase and there are nine different kinds. All told there are 144 different types of influenza A, from H1N1 to H16N9, all of which are found in birds and some of which are also found in horses, pigs, and humans.

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(Information is beautiful)

So why do new versions keep popping up to infect humans? That’s where promiscuous virus behavior comes in. The influenza A virus is fond of a little trick known as reassortment, which means that two viruses infecting the same cell can swap genetic components such as hemagglutinin and neuraminidase proteins. So a chicken in China (virtually all new influenza strains arise in southeast and eastern Asia because of the close contact between humans and livestock) that has two known flu types can give rise to a novel third strain.

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To complicate matters, a virus can mix and match any of its eight genes—not just the H and N proteins—and can incorporate genetic material from swine, avian, and human flu strains.

influenza-h1n1-reassortment (1)

In the case of H10N8, only one person has died and another has become sick, making it much too early to issue any apocalyptic warnings. But Chinese and global health authorities are carefully monitoring the virus—especially any indications that it is transmittable between humans, which is when the alarm bells really start going off.

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