What sort of wild birds are known to have been carrying the virus?
Andy Musgrove: It's not actually fully proven that migratory birds are transporting the virus over large distances, although some of the recent cases in the last few days are making that look increasingly likely. The cases have mostly been in mute swans, but whether it's because mute swans are particularly prone to catch the virus is uncertain. If a mute swan dies it is more likely to be seen than a smaller species, perhaps a small brown duck. So although we're seeing lots of deaths in mute swans it might not be just mute swans that are carrying the virus.
RFE/RL: If migratory birds are not transporting the virus, how else to account for these outbreaks that are geographically far apart?
Musgrove: There are all sorts of ways in which the virus can be transported. There are many documented cases of it being transported through the poultry industry. But the most recent cases, particularly in southern Italy and on the German island in the Baltic Sea, appear to point towards migratory birds being involved. These are well developed countries where one would expect if the virus was present in poultry it would be reported through the normal authorities. In many other countries the reporting structures and the veterinary support is not as well developed and it could go unreported in the poultry industry for some time.
RFE/RL: How predictable are bird movements?
Musgrove: There are two main elements to bird movements to consider. One is the usual annual migration of birds, which broadly speaking is from cold areas to warmer areas so the birds can spend the winters and find enough food to survive, and then back again in the spring. However, there are also more local movements that may be induced by factors such as very cold weather. This is possibly what we're seeing, certainly in the eastern Mediterranean, there's been some very cold weather in the Black Sea region and this is possibly what forced some mute swans and perhaps some other species to Greece and southern Italy.
RFE/RL: Which way are the birds -- and possibly the virus -- likely to spread next?
Musgrove: Now we're in the middle of February and we're coming towards the end of winter. Unless we see any other particularly harsh weather conditions one would expect the majority of movements now over the next few months to be back towards the breeding grounds. So in southeast Europe we'd be talking [of a] more northeasterly [direction] and in north Europe we'd be going east through the Baltics to the breeding grounds in northern Russia and Siberia. I've looked at the weather forecasts for the next five days and it doesn't look like we're going to be getting any further advance of the cold weather fronts across Europe, so in the immediate future there doesn't appear to be too much potential for further spread into northwestern and southwest Europe. All other things being equal, one would expect many of the birds wintering in Western Europe to be starting to move back towards the breeding grounds in the next month or so.
RFE/RL: And potentially spread the virus there too?
Musgrove: If the bird-flu virus had come to the more westerly areas via migrating birds they would have brought it from those countries in the first place, so it wouldn’t' be a new area of infection, it would be going back to the areas they'd come from. However, if the birds have picked it up -- say, in Greece or Turkey or somewhere en route -- from poultry, then potentially they could be able to infect areas that weren't infected beforehand, assuming they can migrate with the virus. It's still uncertain how well wild birds can migrate while carrying the virus because the virus tends to kill them so they don’t tend to migrate very far. The real question is how many birds can carry the virus without it affecting them. This still remains an area of uncertainty.
RFE/RL: Poultry can be kept indoors, but is there any way to contain the spread of bird-flu virus by wild birds?
Musgrove: Not really. The advice is that all the measures should be concentrated around the poultry industry. If the virus is being spread through wild birds the number one thing is to improve your bio-security and keep poultry away from wild birds, particularly in areas where domestic duck and geese make use of ponds. The advice from the [UN] Food and Agriculture Organization and various other bodies is that control of wild birds should not be attempted. First of all it's not really feasible; there are too many birds over too large an area. Second, it's more likely to cause problems by dispersing birds into less usual habitats and outside their normal range of behavior so you're more likely to spread it into areas where it wouldn't otherwise have gone. And thirdly it's a distraction from more useful methods. If you have governments or agencies putting lots of effort into killing wild birds or controlling wild birds, that's probably effort that's better spent in biosecurity.
An expert at the National Virology Laboratory of the Kyrgyz Health Ministry (courtesy photo)
GETTING READY: Many have expressed concern about the ability of Central Asian countries to come to grips with a possible bird-flu outbreak. RFE/RL Turkmen Service correspondent Muhammad Tahir spoke with Erwin Northoff, news coordinator for the UN's Food and Agriculture Organization (FAO), about the issue. ....(more)