One of the world's most respected influenza scientists said today that health officials had been surprised by the spread of swine flu.
Dr Alan Hay, director of the London-based World Influenza Centre, said the extensive summer outbreak in Britain had not followed expected patterns and warned the Department of Health needed to be prepared for a more deadly form of the disease.
"We have been a little surprised by the degree of spread of this virus. A few weeks ago we anticipated that this was going to be a short series of outbreaks that would probably peter out before reappearing in the autumn or winter and that has proved not to be the case."
Hay added:
• Some of the background health concerns noted against flu deaths would not have been fatal, noting an American case where the underlying cause was obesity
• The flu surveillance community had been "caught napping" by the emergence of the swine flu outbreak as most resources were concentrated on guarding against a bird flu pandemic
• He was concerned about the emergence since 2007 of drug-resistant flu, which could impact on the pandemic virus.
Seventeen people in the UK have died after contracting swine flu and 335 people have been treated in hospital after contracting the virus. But tens of thousands are visiting GPs with flu-like symptoms every week, according to the Health Protection Agency. The latest deaths were of a six-year-old girl from north-west London and a GP from Bedfordshire.
Hay, who advises the World Health Organisation on its flu policy, said it had become clear the flu pandemic was predominantly affecting children aged five to 14, with the majority of cases nationally and internationally affecting people under 30. Those born before the 1957 flu pandemic appeared to be particularly resistant to the outbreak, indicating they carried some residual immunity.
Hay said the current outbreak would probably continue for another "week or two" before re-emerging in the autumn and early winter. However, the high level of sufferers now could mean that an autumn outbreak would be less severe.
"We are already experiencing this extensive outbreak of the flu at the present time. The people who are being affected will have reasonable immunity against the virus if it reappears during the winter season, which we anticipate. That will lessen the impact subsequently [on health services]," he said.
"So forecasting what will happen is rather difficult but what the Department of Health has to be prepared for is for there to be significant demand on health services resources."
Of particular concern was that the virus, which has caused only mild illness in most cases, could become more deadly.
"The concern is that the situation might change, the virus may become more virulent," Hay said. "The proportion of severe infections might increase. And fatalities might increase. We have been monitoring this quite intensively in the labs all around the world and have been seeing some minor changes in the viruses."
Hay said there had been a small number of cases of resistance to antiviral drugs but no sustained emergence of resistance.
"We're not totally sure what to expect. Because on the one hand, prior to a year ago, really the anticipation was for very low levels of drug resistance, and then we had the experience in late 2007 with the emergence of drug resistance of seasonal H1N1. And those emerged to become the predominant seasonal virus that has circulated recently. That was really an unanticipated event. We don't know what the implications of that are in the emergence of this novel virus. It is a concern."
Hay concurred that most people who had died from the outbreak had underlying health problems, but said that those may not have been life-threatening.
"Would they have died anyway? I think the answer to that is probably no," said Hay. "Those who have underlying conditions included one that was identified in the US was obesity. So these people were not going to die of obesity in the next month or two I suspect. Some people may have been in a more critical condition."
Flu surveillance scientists, who had been concentrating resources on looking for a bird flu pandemic, had been surprised by the swine flu outbreak, he added.
"We were not anticipating a virus of this nature causing a pandemic. All our eyes were focusing on the H5N1 virus that had been circulating in wild and domestic poultry populations.
"We have been observing similar viruses to this pandemic in pigs in the past 10 years in the US. And because it was antigenically related to the viruses already circulating – it was the same H1N1 subtype – it was not perceived as being a major threat. Of course we were caught napping, you might say, but this is what has transpired.
"We don't really know the way this virus might change as it adapts to the human population and what the consequences of such changes might be."
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