Mutant bird flu virus still as deadly as first thought

Debora MacKenzie, consultant

(Image: Quirky China News/Rex Features)

The battle over bird flu continues. As you may recall, researchers in Rotterdam, the Netherlands, have answered the two biggest questions about H5N1 bird flu: yes, a few mutations can make it readily transmissible between mammals; and no, the transmissible virus is not less deadly than the H5N1 we have now, which is hard to catch. New Scientist had the story when it was first reported at a scientific meeting in Malta last year.

Now, there are reports that Ron Fouchier, leader of the Rotterdam team, has told a meeting in Washington DC that the transmissible H5N1 wasn't all that deadly after all. What's going on?

What's going on is the continued dispute about whether the work can be published. The US National Science Advisory Board for Biosecurity (NSABB) advised against publishing details that an evildoer could use to make a nasty bioweapon. The journal involved, Science, agreed to the advice, but only if those details could be confided to public health agencies and other flu researchers. Last month, a group of flu specialists - including the chair of the NSABB - met at the World Health Organization and decided there was, unfortunately, no way to arrange that.

So what happens now? Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, which funded the work, has found a way through the impasse. He explained to a meeting on defence and biosecurity in Washington DC this week that there is now new information about the study that the NSABB should consider. A revised paper will be given to the committee soon.

Fouchier presented the new information at the Washington meeting. Nothing in his talk contradicts the story I heard in Malta, although it may refute some of the more hysterical interpretations of it. You just have to listen carefully.

Fouchier says the seven ferrets that caught the mutant H5N1 via aerosol transmission from other ferrets got sick, but didn't die. Moreover, only one of eight ferrets that had a large dose of the mutant actually put up their noses died. In contrast, ferrets which got the ordinary, wild-type, pre-mutation H5N1 in their noses all died. This certainly makes the mutant seem a wimp.

Actually, though, it's the wild-type virus that's odd. In general, when you give ferrets most kinds of H5N1 in their noses, said Fouchier, "they don't get sick at all". The strain he used, collected in 2005 in Indonesia, is known for causing unusual brain-related disease when put in ferrets' noses. Perhaps the mutant has lost this: the ferrets who got it in their noses, either by breathing it in or because it was put there, just got flu.

It's what H5N1 does in lungs that matters for us, because that's how it kills us. The Rotterdam group says putting flu viruses in the ferret's windpipe, or trachea, is the "appropriate model of infection in humans". And there the mutant, transmissible H5N1 was just as deadly as the wild one -? just as Fouchier said in Malta. All the ferrets died.

Evidently the few ferrets so far exposed via aerosol didn't get enough virus in their windpipes to kill. But the virus has done the hard part: it's a shorter jump from nose to throat than from ferret to ferret. And we don't know how any of this plays out in people. So this still means H5N1 is a threat.

Fouchier also argues that his mutant virus wouldn't sweep the world if it escaped, as it doesn't spread as efficiently as the swine flu that went pandemic in 2009. That's not surprising: swine flu was fully adapted to mammals, H5N1 is a bird flu with a few mutations - that it can spread via aerosol at all is news. But such a virus would spread, and adapt, given a chance.

Finally, he says we're safe because ferrets first exposed to ordinary flu don't later die of wild H5N1. This is actually really important work, which we reported when it had still only been done in mice: it means having the flu gives you immunity to more kinds of flu than flu vaccine does. Most people have had flu. So are we safe from this thing after all?

Hardly. If having had flu protects you from wild H5N1, why have 348 people (at last count) died of it? Had none of them ever had flu? Unlikely. That cross-reaction may have protected some experimental ferrets from H5N1, but apparently it isn't enough for all of us.

If transmissible H5N1 wasn't worrying, we wouldn't be continuing the moratorium on research until, as Fauci also said in Washington, we've seen to the "fortification" of lab safety. That's welcome news - as long as the research resumes, safely, soon.

Source: http://feeds.newscientist.com/c/749/f/10897/s/1d18a828/l/0L0Snewscientist0N0Cblogs0Cshortsharpscience0C20A120C0A30Cmutant0Ebird0Eflu0Evirus0Estill0Eas0Bhtml0DDCMP0FOTC0Erss0Gnsref0Fonline0Enews/story01.htm

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