The Truth About Bird Flu

Bird flu outruns the vaccines

04 November 2006

A NEW strain of H5N1 bird flu has emerged in China and is poised to start yet another global wave of infection. The human pandemic vaccines now being developed will not protect against it. Worse still, nearly three times as many Chinese poultry are infected with H5N1 now as last year, meaning there is a greater chance of human infections - despite China's insistence that all poultry be vaccinated against it. In fact, vaccination may be to blame for the new strain.

“ The human vaccine now being developed would not work against a virus descended from the new strain ”

Yi Guan and colleagues at the University of Hong Kong have been testing poultry in markets across southern China for bird flu for years. In 2004, 0.9 per cent of market poultry tested positive for H5N1, including 2 per cent of ducks, a major carrier of the virus. But between the middle of 2005 and June this year the virus turned up in 2.4 per cent of market poultry - a nearly threefold increase - and 3.3 per cent of ducks. The virus is also showing up in chickens for 11 months of the year, up from only four months previously.

The reason, says Guan, is a new "Fujian-like" strain of the virus, descended from one first seen in a duck in Fujian, China, in 2005. It caused 3 per cent of poultry infections in September 2005 but was responsible for 95 per cent of infections by June 2006. "The predominance of Fujian-like virus appears to be responsible for the increased prevalence of H5N1 in poultry," write Guan and colleagues in a study published in the Proceedings of the National Academy of Sciences this week (DOI: 10.1073/pnas.0608157103).

“ The new 'Fujian-like' strain caused 3 per cent of poultry infections in September 2005 and 95 per cent by June 2006 ”

A higher number of infected but apparently healthy birds in Chinese markets for more of the year means a greater risk for humans, says Guan. All but one of China's 21 officially reported human cases of H5N1 have occurred since November 2005 - after the Fujian strain started its rise. Some of these people lived far away from any known outbreak in poultry, but close to urban poultry markets, suggesting the new strain is spreading silently in some of the world's most crowded cities.

Based on what previous H5N1 viruses have done in China, Fujian now seems poised to start a third epidemic wave, potentially worldwide, following the first in 2004 and H5N1's spread across Eurasia in 2005. So far the Fujian virus has reached Thailand, Malaysia and Laos.

Its sudden emergence suggests that a selection pressure is acting on the virus. In November 2005 China ordered compulsory vaccination of all poultry. The law has been imperfectly applied, however: Guan and colleagues found vaccine-induced antibodies in only 16 per cent of birds tested. What's more, they found these antibodies do not recognise the Fujian virus, even though they attack the previous strains of H5N1. "This novel variant may have become dominant because it was not as easily affected as other strains by the current avian vaccine," Guan says.

In 2004, an investigation by New Scientist concluded that vaccinating poultry against bird flu can lead to the emergence of novel strains that can circulate undetected in vaccinated birds unless there are scrupulous controls ( New Scientist , 27 March 2004, p 6). The risk is that whatever strain emerges might have unexpected features, such as an ability to kill humans.

While Guan's team has no evidence to suggest that the Fujian strain is more virulent or likely to transmit between humans than previous strains, so far it has killed one person in Thailand and caused five of the Chinese cases for which the team has virus samples. "As far as I know all (20) human cases since November 2005 were caused by this virus," Guan told New Scientist .

The discovery is a warning bell to researchers working on human vaccines for H5N1. The pandemic vaccine now being developed by pharmaceutical companies is based on strains of H5N1 isolated from Vietnam in 2004 and Indonesia last year - but antibodies to these strains do not recognise the Fujian strain. This means the vaccine would not work against any pandemic virus carrying surface proteins from the Fujian strain.

From issue 2576 of New Scientist magazine, 04 November 2006, page 8-9

Behind enemy lines

THE sudden emergence of a "super-strain" of H5N1 that sweeps away all other strains may seem unsettling, but it is something we could have predicted. Human flu does this all the time. The reason people get flu year after year is because the virus evolves slightly different surface proteins that our immune systems don't recognise from the last time we had flu.

Researchers had thought this was a continual process, with individual mutations being selected for if they give the virus an advantage over the others. Now David Lipman and colleagues at the National Institutes of Health in Bethesda, Maryland, have shown that the process is far more sporadic.

Using a large collection of recent flu strains, they showed that H3N2, the most common human strain, generally floats in evolutionary limbo accumulating random mutations, none of which gives any virus an advantage over the rest. As more and more people become immune, flu seasons become milder.

Then every few years, one virus happens to collect a winning combination of these individually useless changes that enables it to avoid recognition by human flu antibodies. It out-competes other H3N2 viruses and rapidly becomes the dominant strain that sweeps the world ( Biology Direct , DOI: 10.1186/1745-6150-1-34).

In 1998, for instance, one strain from Australia acquired a novel surface change, but it wasn't until 2003, after a few more key mutations, that it suddenly emerged as the most murderous H3N2 of recent years.

Lipman's team suggests that by monitoring these random mutations, we might learn to predict what dominant strain is about to emerge, giving vaccine makers more warning.

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New strain of H5N1 bird flu emerges in China

22:00 30 October 2006

A new strain of H5N1 bird flu has emerged in China that is poised to start yet another global wave of infection.

Nearly three times as many Chinese poultry are infected with H5N1 now than last year, despite China's insistence that all poultry be vaccinated. In fact, vaccination may be the reason for the increase in infections, researchers say.

The reason, the researchers say, is a new “Fujian-like” strain of the virus, descended from one first seen in a duck in Fujian, China, in 2005. It caused 3% of poultry infections in September 2005, but 95% by June 2006.

Unrecognised cases

More infected – yet apparently healthy – birds in Chinese markets for more of the year means more risk for humans. All but one of China's reported human cases of H5N1 happened after the Fujian strain started its rise, and some lived far from any known outbreak in poultry, but close to urban poultry markets.

The team has no evidence that the virus is more virulent or more likely to transmit among humans than previous strains, he says. But it has caused one human death in Thailand, and the five Chinese cases for which the team has virus samples. “As far as I know all 20 human cases recognised since November 2005 were caused by this virus,” Guan told New Scientist

Based on what previous H5N1 viruses in China have done, the team warns, the Fujian strain seems poised to start a third epidemic wave, after the first in 2004, and H5N1's spread across Eurasia in 2005. Fujian virus has so far spread to Thailand, Malaysia and Laos.

Surging infection

In November 2005 China ordered compulsory vaccination of all poultry. The law has been imperfectly applied – Guan and colleagues found vaccine-induced antibodies in only 16% of the birds they tested. But they also found that those vaccine-induced antibodies do not recognise the Fujian virus, although they do attack the virus strains that Fujian has now replaced.

This means the Fujian strain has a selective advantage in vaccinated birds. “This novel variant may have become dominant because it was not as easily affected as other strains by the current avian vaccine,” says Guan. That may also be why H5N1 infection in Chinese poultry has surged, rather than decreased, despite increased poultry vaccination.

Worryingly, the antibodies being used to develop human vaccines for H5N1 have been induced from 2004 strains of the virus – these antibodies do not recognise the Fujian strain. This means the current experimental pandemic vaccine would not work against any pandemic virus that emerged equipped with Fujian surface proteins.

Journal reference: Proceedings of the National Academy of Sciences (DOI:0:1073/pnas.0608157103)

____________________________________

Here we go again:

BBC headline 18th September 2006: Surveillance Checks For Bird Flu
"New tactics are being adopted in an attempt to prevent an outbreak of Bird Flu in Britain.
A surveillance operation will to check for infected birds will concentrate on favourite spots of migrating wild fowl
The operation will also focus on poultry farms which could be at risk from the H5N1 bird flu virus."

Comment: Oh for goodness sake! All over the world there are places where bird flu is endemic amongst birds - and only rarely infects people who live in close proximity to them. This is going to lead to completely exaggerated responses to any report of a bird looking off-colour. Newsreel film of thousands of birds being slaughtered will be used to convince us that we are being protected, when nothing could be further from the truth. What is needed is international surveillance of infections in human beings, to try to spot early signs that the virus has mutated to the dangerous form where it will transmit human-to-human. And some preparations for limiting any epidemic if and when it hits this country. As yet, there is nothing but window dressing.
If the current British government ever got to be Really Thick, that would be an improvement...

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Bird flu outruns the vaccines

Behind enemy lines

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Unrecognised cases

Surging infection

Here we go again: