The H5N1 avian influenza virus has not yet reached North and South America. What will happen when it does? Declan Butler and Jacqueline Ruttimann investigate.
The H5N1 virus once seemed a problem that was lurking in someone else's backyard farm. But since last summer, the lethal avian influenza virus has surged out of southeast Asia into Europe, the Middle East and Africa. Fifty-one countries — 36 this year alone — have now experienced outbreaks.
The New World is as yet untouched, but many experts consider it inevitable that the virus will reach North and South America. This area is home to the world's largest poultry exporters, Brazil and the United States. And although government and industry officials say they are well prepared for the arrival of H5N1, others argue that they have yet to take on board the full extent of the challenge.
“When H5N1 arrives,” says Mark Cackler, the World Bank's agriculture manager for Latin America and the Caribbean, “it will concentrate minds wonderfully.”
Trade, smuggling and migratory birds are all potential routes for H5N1 to reach the Americas (see page 138). How it arrives is ultimately less important than stopping a subsequent spread of the disease, says Juan Lubroth of the UN Food and Agriculture Organization. And here there is no debate as to what causes spread, he adds: it's not migratory birds, but “human actions, trade and husbandry practices”.
Experience in Asia and Europe provides best practices on controlling avian flu, says Jim Butler, director-general of the Inter-American Institute for Cooperation on Agriculture in San Jose, Costa Rica. “We don't need to reinvent everything.” The task for the Americas, he says, is more about “building consciousness” of the risks and existing best practices.
Such practices include setting up surveillance and diagnostic capacities that can quickly detect any initial outbreak. But despite all best efforts, some virus will always go undetected, so countries must also have policies in place to make their farming systems more resilient.
Such policies can be as simple as requiring the poultry industry to disinfect all material and people moving in and out of farms. Another is to reorganize national poultry industries into regional ‘cells’ that operate independently of one another, so that if one goes down with H5N1, the others do not.
France prepared by using both approaches, and so far the H5N1 found there has been stopped in its tracks. Turkey did neither well, and has suffered persistent outbreaks. The well-developed animal health services in the United States and Canada have implemented similar measures to those in France, and are widely expected to quickly contain any outbreak of H5N1.
Unlike regions of southeast Asia and Africa, where poultry live outdoors and mingle freely with each other and with wild birds, US flocks are highly concentrated in industrial farms, where birds are raised indoors, isolated from external contaminants. One potential weakness is the popular live markets in California and the northeastern states. In the northeast, these markets have sustained an avian flu virus of low pathogenicity, H7N2, since 1994. In the past, as many as 60% of birds sampled have carried flu viruses, although control measures have reduced the levels.
Such live markets “continue to be a major source of avian influenza viruses and a risk for introduction to commercial poultry operations”. This is what David Swayne and David Suarez of the US agriculture department's main poultry research laboratory in Athens, Georgia, told an influential 2004 workshop on pandemic planning that was organized by the US National Academies.
South America is also preparing well, experts say, as it has decades of experience of handling other highly contagious diseases, such as foot-and-mouth disease. Lubroth gives the continent good marks for “high awareness favouring quick detection and response”.
Brazil's poultry industry is both larger and more complex than that in the United States. Backyard farms are common in the poor northeastern part of the country, and smallholdings are scattered throughout urban areas and along the Amazon. But its core production remains in large commercial farms, which are well aware of the economic risks of H5N1, says Lubroth. “If H5N1 entered,” he predicts, “they would stamp it out quickly to preserve the main industry.”
That view is overly optimistic, argues Cackler, who sits on the avian-flu taskforce for the World Bank. Many South American countries, he says, have only recently woken up to H5N1 as something they might need to worry about. He recalls speaking to the agriculture minister of “one to-be-unnamed country” last November, who “just didn't get it; H5N1 was nothing to worry about”. Cackler met him again in January, after H5N1 had ripped across Europe. “This time, the guy got it.”