The current swine flu pandemic is less severe than might be expected, says the European Centre for Disease Prevention and Control (ECDC). The ECDC has published the planning assumptions that European countries could use to prepare for the major first pandemic wave expected in the coming autumn and winter months. The Centre has drawn heavily on the planning assumptions put out by Britain’s Cabinet Office and its Department of Health last month.
The swine flu’s death rate, known as the ‘case fatality ratio’, is expected to be similar to that of seasonal flu that people catch each year.
Peak absenteeism:
The British had predicted a peak absenteeism rate of 12 per cent of the workforce, which fitted with the mild illness seen for most people, observed the ECDC. This suggested that “the social disruption effects of the pandemic will be less than feared for other pandemics and that severe social interventions will not be necessary given good business continuity planning,” it remarked.
‘Hope for the best and plan for the worst’ is at the heart of much contingency planning. The ECDC and British planning documents give a glimpse into what ‘the worst’ in the current pandemic, involving a virus that the World Health Organisation describes as moderate in its severity, might be like. The British planning document is based on analysis and modeling of data from swine flu outbreaks that have occurred both inside and outside the country.
Both ECDC and U.K. documents emphasise that the planning assumptions they describe should not be seen as a prediction of how the pandemic will develop. A number of parameters were involved, each taken at their ‘reasonable worst case’ value, noted the British document.
Taken together, these parameters “represent a relatively unlike scenario.” However, the use of such parameters ensured that the plans remained robust against all likely circumstances, it pointed out.
In order to plan for extreme contingencies, the British document assumed that up to 60 per cent of the population could catch the virus. But about half of them may show no or insignificant symptoms.
Up to 30 per cent of the population may therefore become clinically ill in the first major wave of infection. Children are more likely to be ill than older people. However, the latter are more likely to suffer from complications if they do become ill.
“Shoter and Sharper”
The British planning document indicates that 6.5 per cent of the population could fall ill each week at the peak of the pandemic. But since local epidemics are “often shorter and sharper,” the proportion of the local population that falls sick could be higher than national rates, the ECDC noted.
The document also suggests that up to 2 per cent of clinical cases in Britain might require hospitalization, a quarter of whom could need intensive care. Hospitalization rates for seasonal flu that occurs every year are typically in the range of 0.5-1.0 per cent for that country. However, the case fatality ratio – the proportion of clinical cases who die of flu during the complete wave of infection – is expected to be in the same range as for seasonal flu, 0.1 -0.35 per cent. “Current experience from abroad suggests a figure closer to 0.1 per cent at present,” the document observed.
“It is also important to appreciate that [the case fatality ratio] is especially subject to social effects,” the European centre remarked. In poor social settings such as Africa, even seasonal flu could result in death rates that were higher than seen in pandemics, it pointed out.
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