Within a week of it first being identified, cases were found in Europe: initially in Spain and Scotland. Further cases were imported into the UK from Mexico and the US during May and June which resulted in isolated outbreaks (largely in schools) and an awful lot of public health and press interest. That it was a new flu virus and that it was clearly transmissible caused considerable concern. WHO declared a pandemic on 12th June. It was difficult to assess the severity of the strain of flu as so few cases had occurred outside Mexico, and the data from Mexico were difficult to interpret since alarm had caused large numbers of people (including the “worried well”) to seek care at hospitals and health centres for otherwise mild illness. Very few of these cases were tested. Nevertheless, it appeared that the illness was no more severe than seasonal flu. It was also apparent very early in the epidemic that older individuals appeared to have some degree of protection. 

Increasing numbers of cases were occurring in the UK, and by the middle of June the Health Protection Agency had given up trying to offer antivirals (usually tamiflu) to every case and the contacts of these cases. Indeed, by this time it was no longer possible to test and count every suspect case, and the authorities started using counts of “influenza-like-illness” (ILI) seen by doctors as a measure of the epidemic progress. By the end of June it was clear that swine flu was spreading all over the UK and that school children were the focus of the epidemic. Surprisingly no other country in Europe had a significant outbreak, even though most countries had imported plenty of cases. Why this was the case is an ongoing mystery.

Another major surprise was that we were getting a major epidemic in the summer – most experts believed that as flu seems to be seasonal, we would not get a major outbreak until the autumn. Indeed by this time southern hemisphere countries like Australia and New Zealand were all experiencing widespread epidemics.

The epidemic was widespread in July, causing considerable alarm and much interest in the press. And then another surprise happened. The schools closed for the summer holidays and the epidemic quickly started to diminish. Most experts had thought that school closure would have some effect, but the scale of the impact was dramatic. Source: HPA

At first it was difficult to work out whether the decline was due to the schools closing or the launch of the NPFS (the online and telephone antivirals service), but we were able to show, using results from flusurvey that the decline was real.  

Flusurvey results continued to surprise us over the summer. It was clear very quickly that there were some fairly astonishing changes underway in the way that people dealt with their infections. In the early part of the epidemic (June and July) people were far more likely to contact their doctors and far more likely to take antivirals, as well as far more likely to take extended periods of absence than later on. Perhaps people were becoming less concerned about swine flu, as the gloomy scenarios that had been mentioned during the early part of the epidemic (e.g. 60,000 deaths) appeared increasingly unlikely.

When schools returned in September the epidemic started to take off again. This time, however, it also appeared to take off in other European countries as well. The focus had now shifted to vaccination. The UK had ordered around 100 million doses of vaccine (enough to vaccinate almost everyone with 2 doses), but the vaccine was not due to arrive in sufficient numbers until the autumn. There was now a race on to vaccinate people before the virus got to them first.

Vaccination of high risk people started at the end of October, just as the epidemic peaked (again, half-term had an effect on the peak, causing a little second bump when the schools re-opened). As it turned out, vaccination of high risk people was far slower than anticipated and a far lower level of coverage was achieved - by the end of December about half of the at-risk population had been immunised.

Plans were made to extend the vaccination programme to low-risk children under the age of 5 years, but ongoing disputes about how much GPs should be paid to vaccinate slowed this programme down considerably. Plans are still being made to vaccinate these children even though the epidemic is virtually over.

So what next? Who knows. Will there be a third wave of swine flu? It seems unlikely, but it is possible. Will there be a seasonal flu wave this winter, or has the pandemic strain caused the other strains to go extinct? Or will the seasonal epidemic just be delayed a bit? What will happen next year? Will swine flu mutate and become a seasonal strain? Will it become more severe? Will the existing seasonal strains come back? We simply do not know. Please continue to help us address these questions by logging on and telling us whether you have any symptoms or not. Once again, the data provided by flusurvey users will be pivotal in answering these questions.