Can you explain what a grade four alert means - this is the World Health Organisation - we're on a grade four alert - and how does that compare to the threat that was posed by avian flu over the last few years?
Well the pandemic alert come from one to six, if you like, and we have been sitting at level three for some time because of what we've been seeing in the Far East, particularly about avian flu but this change has moved us up one level, there's still another level to go before we actually hit pandemic level six, which is when a pandemic itself arrives. So we've moved a step closer but it is not yet inevitable and there is another step, if you like, between now and the pandemic itself.
And in terms of practical advice that you're giving to hospitals and doctors does it make any difference whether we're on grade three or grade four in actually the management of suspected cases?
To be honest not a huge difference. The difference between level three and level four is the emergence of a virus outside the UK that shows potential to spread from person to person. When it starts spreading very rapidly from person to person we go to five and then we go to level six. So it doesn't change a lot of the planning that we've done and advice we give, it just gives us a certain air of urgency.
Your area is - responsibility is London, have you had many cases of people contacting their GPs or indeed hospitals over the last day or two?
We've been quite busy on the phones here in the Health Protection Agency and I'm sure that's reflected in both hospitals and the GP work around London. A lot of people have been travelling who are now a bit worried about it. Most of the calls we get turned out not to have any real connection with swine flu but obviously it's people who have been concerned and we need to reassure them.
Well the first step in any potentially serious flu outbreak is to confirm the diagnosis as soon as possible. Dr Alan McNally is a senior lecturer at Nottingham Trent University and part of a European team working on portable testing equipment that can identify the causative virus within just two hours.
For a standard viral infection generally what you would do is you would present to your GP, he would either take some blood samples or a swab. In the case of influenza generally a throat swab or a nasal swab and that would be transported to a hospital lab and the hospital lab would do some antibody based testing or looking directly for the virus. And more and more so now laboratories are using molecular tests - so looking for the virus's genetic material. And as long as the virus is well characterised - the virus that you're looking for is well known - that's a fairly straightforward process. Obviously the problem with this new swine flu, as it's been tagged, is that genetically it's very different from anything we've seen before, which means that even using things like antibody based detection is very difficult because it's a new virus essentially. So we have to design tests from scratch again to detect this new virus.