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Durham University experts comment on swine flu

(1 May 2009)

Durham University experts have commented on the recent outbreak of swine flu.

Expert in microbiology and viruses at Durham University, Dr Paul Yeo, answers frequently asked questions on swine flu. 1. What is the science behind how new flu strains arise – this one has pig, human and bird components (mainly pig)? Viruses change and can undergo enormous change at a rapid pace; they are in that sense ‘clever’ and it can only takes a few changes for a pig virus to adapt to a human. The pig has been considered the mixing bowl of influenza viruses, both avian flu and pig flu viruses have spread via the pig to humans. The problem now with this virus is that it has now picked up a mixture of elements, now including human elements; it’s a complex virus. Flu strains change and mutate, they are very adaptable. 2. Why is the testing taking so long? Are they re-testing samples? Delays in testing could be perceived delays and these may simply be due to the fact that people are unrealistic about timescales. It takes time to check, test and validate tests. There may be only a few places in the world where you can do this form of testing. It takes time. 3. How long will it take to come up with a viable vaccine for this particular strain of flu? It is likely to take at least 6 months to build up enough stocks of the vaccine. You have to grow enough of the virus culture, and then develop and build up stocks of a vaccine. The culture is grown in special, pathogen-free chicken eggs that have to be kept in sterile conditions in specialised facilities, in constant temperature rooms. These eggs have to be inoculated with the virus and the culture developed. You need lots of eggs and room to store them, and enough people to check and test the eggs. Then there’s the issue of processing the vaccine and checking that it’s safe. 4. How much potential does this strain have to alter as it spreads? Swine flu can alter as it spreads - it’s a virus and that’s what a virus does, they mutate and change and, for example, that’s why we need a new influenza vaccine every year. 5. Why has it so far proven deadly in Mexico but far less so elsewhere, even if the infection rates are on the rise? There’s no clear answer to this – if we knew the answer, it would be like finding ‘the answer’, the holy grail of virology. 6. How much of a threat does swine flu pose? We have to wait and see. It is very early days but it’s not hype if people are dying in large numbers. The worrying feature here is that we have a virus that has jumped species; it has spread from animal to human. In avian flu, the outbreak was contained to a large extent. It didn’t jump from human to human. Swine flu has jumped species and is now spreading from human to human; that’s a significant change. 7. The two confirmed cases in Scotland have not shown any symptoms for more than 24 hours now, why are they still in isolation? What can be learned from their cases? There is a need for safe period once someone is diagnosed with swine flu, even though they may seem to be better, the virus may still be in the patient and they could still transmit it. 8. I am hearing conflicting messages about transmission and symptoms. Some people are saying you can’t shed the virus unless you have symptoms and other people are saying you can transmit it for up to seven days before showing symptoms. Environmental archaeologist and expert in the history of pigs, Professor Peter Rowley-Conwy, says diseases such as swine flu have existed for thousands of years. Prof Rowley-Conwy said: “Humans have been picking up diseases from pigs and other animals ever since we domesticated them 10,000 years ago, and started to live in close contact with them. “Swine flu is just the latest example of a very old phenomenon. Village communities started to domesticate pigs both in China and the Near East around that time. In Eurasia we have now lived with goats, pigs and cattle so long that we have developed a tolerance for the diseases we have picked up, such as tuberculosis, influenza, smallpox, and measles. “When Europeans contacted people without this tolerance, such as Native Americans, Australian Aborigines, Pacific islanders, these diseases had a significant effect on them.” Prof Rowley-Conwy led the Department of Archaeology’s PIG PROJECT, which has looked at bones, DNA (ancient and modern), and various other aspects of pig-human relations over the last 10,000 years.