1.4 Previous flu pandemics
Three times in the last century, influenza A viruses have undergone antigenic shift resulting in pandemics with large tolls in terms of both disease and deaths.
Table 1.3 Pandemics during the last century
| Pandemic | 'Spanish Flu' | 'Asian Flu' | 'Hong Kong Flu' |
|---|
Strain | A(H1N1) | A(H2N2) | A(H3N2) |
|---|
Year | 1918-1919 | 1957-1958 | 1968-1969 |
|---|
Likely origin | Not known (first cases identified in Europe and USA) | China | China |
|---|
| Estimated deaths: | | | |
Global
UK
| 20-40 million
250,000 | 1 million
33,000 | 1-4 million
30,000 (England and Wales) |
|---|
Age group most affected | Healthy young adults (20-50 years) | Very young and very old | Very old and those with underlying medical conditions |
|---|
1.4.1 Using past pandemics to estimate the impact of future pandemics
Most estimates of the impact of a future pandemic are based on extrapolations from previous pandemics. However, it is important to remember that significant details of these events are still disputed, in particular the true number of deaths. Secondly, predictions based on previous pandemics need to take into account the fact that the modern world is very different from 1918, for example: since then there have been considerable improvements in nutrition, health care and opportunities for interventions. It is, therefore, important to understand that all impact predictions are estimates and that the actual impact of the next pandemic may turn out to be very different. The likely impact of the next flu pandemic is discussed in further detail in Chapter 4.
1.4.2 Where will the next flu pandemic originate?
While a new pandemic strain of the flu virus could first emerge anywhere, including the UK, it is most likely to emerge in China and the Far East, as most previous pandemics appear to have done. In this part of the world, dense human populations, domestic pigs and wild and domestic birds live in close proximity, facilitating the mingling of human and animal viruses through co-infecting and the consequent genetic exchange that could give rise to a pandemic strain.
