Flu pandemic would peak in UK within four months
Within two months of the first pandemic flu case anywhere in the world, it would arrive in the UK. It would peak here two months later with countless thousands likely to have died, but the worst would be over within four months.
That is the most likely scenario for a flu pandemic, according to results of the first computer simulation of how the virus would spread across the country.
Neil Ferguson of Imperial College London, who led the study, said the illness rate could be halved if there were enough drugs for half of the population. This would require a doubling of the planned stockpile of anti-viral drugs.
He believes the pandemic could be slowed if schools were closed and people living in the same household as those infected by flu also took anti-viral drugs. He suggested stockpiling vaccines, even though the exact strain of flu that will become a pandemic had not been identified.
The government's current plans include ordering 14.6m courses of anti-virals by September, enough for a quarter of the UK population. There are plans to buy 120m doses of vaccine for whichever strain of flu ends up becoming a pandemic infection.
Sir Liam Donaldson, chief medical officer, said he welcomed the research. "Our pandemic flu strategy is based on advice from the scientific advisory group. A strategy of household prophylaxis will be considered alongside other possible measures. We will continue to work with Professor Ferguson to explore the other options that could protect the public."
Prof Ferguson's computer model, developed in conjunction with the Johns Hopkins Bloomberg School of Public Health and RTI International, built up a virtual population of UK inhabitants on a computer, and, using real data, simulated their interactions at work, school and in homes. "We layer on top of that an epidemic process, which says something about what the biological characteristics of a disease are, how long people are sick for, how long they incubate for, how infectious are they," he said.
The computer simulation showed that treating flu-stricken people would reduce transmission but only if anti-viral drugs were given quickly, within a day of the symptoms first appearing. Vaccines would also need to be available within two months of the start of the pandemic to have any major impact on the spread of the disease.
This is impossible using current manufacturing methods, which require up to six months to produce vaccines after a flu strain has been identified.
"We should seriously consider stockpiling some vaccine ahead of the pandemic," said Prof Ferguson, whose study appears in Nature today. The Department of Health said any decision to stockpile vaccines would be carefully considered.
Prof Ferguson said that, while the UK was ahead of the curve in stockpiling anti-virals and vaccines, the logistics of making the drugs available was a major factor in controlling the spread of pandemic flu. "We need more emphasis on how we would actually deliver these things in a pandemic," he said.
Current government plans suggest the ill should be treated within 48 hours of developing symptoms. But this target might be shifted to offer treatment within 24 hours in light of the new models. Prof Ferguson said emergence of the H5N1 avian flu in recent years meant the authorities should be prepared for the worst. "H5N1 is not any more likely to cause a pandemic but if it did, the likelihood is that it would cause a more lethal epidemic than other bird flu strains," he said.
The report coincides with publication of an 18-month government investigation into the threat new and emerging infectious diseases will pose to Britain over the next two decades.
At the launch of the document, Sir David King, the government's chief scientist, warned that international travel, trade, changes in land use and global warming would continue to bring diseases to Britain.
But the report, which drew on the expertise of 300 scientists from 30 countries, claimed that new technologies to spot outbreaks of disease early would dramatically cut death rates, avert the need for mass animal cullings and save billions of pounds in battling infectious diseases.