The killing of 40 million chickens and other birds by US farmers, have caused egg prices to soar as a deadly version of the avian flu attacks the poultry industry.

An outbreak of a particularly infectious version of the bird flu, believed to come initially from wild ducks and geese, has spread into 15 US states and two Canadian provinces, requiring the mass slaughter of egg-laying chickens and turkeys in particular.

That has turned into an 80 percent surge in the wholesale price of eggs, and a more modest hike in turkey meat costs, which could last for the rest of the year even if the flu outbreak can be successfully contained, according to industry officials.

Vaccination a Culprit

Earlier this month there were mass reports of bird flu rampaging across the Midwestern US. At that time 13 million chickens and turkeys were culled or earmarked for destruction to stop the spread of H5N2, an offspring of Asia’s H5N1 bird flu.

Vaccinated poultry spread the virus without getting sick, making its spread invisible. Vaccination has moreover driven the evolution of H5N1 as these viruses adapt to the vaccinated birds.

The midwest state of Iowa, the largest US egg producer, has seen some 25 million birds, mostly chickens for egg production, killed.

The state has declared a state of emergency against the disease, and after discovering avian flu on a 63rd farm, on Thursday banned any public exhibition of live birds, including at fairs, auctions, swap meets and other events.

In late 2009, virologists and influenza authorities were becoming increasingly concerned that the A-H1N1 flu virus could “reassort” with the highly virulent H5N1 avian flu that’s still prevalent in parts of the world like China, and that a mutation could occur resulting in a new strain that has the lethality of H5N1 and the human transmissibility of A-H1N1.

“H5N1 virus has never acquired the ability to transmit among humans, which is why we haven’t had a pandemic. The worry is that the pandemic H1N1 virus may provide that nature in the background of this highly pathogenic H5N1 virus,” says Kawaoka, a professor of pathobiological sciences at the UW-Madison School of Veterinary Medicine.

Two viruses infecting a single host cell can swap genetic material, or reassort, creating hybrid strains with characteristics of each parent virus.

Three vaccines used to prevent respiratory disease in chickens have swapped genes, producing two lethal new strains that have killed tens of thousands of fowl across two states in Australia

The creation of the deadly new variant was only possible because the vaccines contained live viruses, even though they were weakened forms, said Joanne Devlin, lead author of the paper published in the journal Science.

“The scale of this outbreak has been unprecedented, so we think it is important we take every possible step to limit the chance that this disease will spread any further,” said Iowa Secretary of Agriculture Bill Northey.

Wild birds Also a source

The disease first surfaced last year in the far northwest state of Washington, assumed to be transmitted by wild birds although that was never confirmed.

Since then it has appeared in farms in 15 states, including some of those with the largest poultry industries.

The US Centers for Disease Control says the risk of H5N2 jumping to humans is “low at this time,” though it does not rule out the possibility.

Figures from the US Department of Agriculture show that more than 39 million birds had been infected by or exposed to the new strain of bird flu as of this week.

“While the role of wild birds as reservoirs and vectors of the virus has been highlighted in these various epidemics, other factors of transmission, especially among poultry farms, could rise to prominence unless appropriate precautions are taken.”

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