More animals and a nastier virus than the last time

The 1967 Epidemic
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Why is this epidemic so much worse than 1967?

Why is this epidemic so much worse than 1967?

The virus is different

The variant of the virus Picornaviridae, which causes the disease, is a comparatively small bundle of just 8,200 "base pairs" of RNA, its reproductive material, wrapped in a protein coat. Its small size and ferocious reproduction means that it mutates very rapidly; potentially, one pair can mutate with every reproduction.

Most of these mutations will not survive, but given enough time the virus will reach a version which infects animals more rapidly than its forebears.

The 1967 virus had to incubate in an animal for about seven days before it could infect another. The "generation time" is much shorter in this year's version - just two days, it is believed. However, it still takes many days for animals to begin to show symptoms. Thus the virus spreads by stealth.

There are more animals

The Common Agricultural Policy (CAP) pays farmers a subsidy for animals according to the size of their herds and flocks, not the size of the land on which those animals feed. The Soil Association, which lobbies for organic farming, says this encourages crowding that promotes the spread of the virus by contact.

"Compared to 1967, at the same time in the epidemic, there were more cases then, but on smaller farms," said Lawrence Woodward, who has studied the scientific arguments for and against vaccination. "Controlling and localising the disease today is far more difficult."

The association said that it will press for the CAP to move from a herdage-based subsidy to an acreage-based one. Such a change would take years.

There are more animal movements

Trading of animals up and down the country is more commonplace today because transport costs are generally lower. That has led to more animal contacts, which has spread the disease throughout the country; the multiple outbreaks so widely spread around the UK are testament to this.

There is more international animal trading

In some cases, pigs are exported to France and subsequently re-imported to Britain for slaughter as "French meat". That means that animals incubating the disease could have passed over the Channel - as has been confirmed by the outbreaks in France and the Netherlands.