Swine flu death rate estimates 'flawed'

London, July 15 (ANI): The current estimates of the proportion of people who would die if infected with swine flu are flawed, according to researchers in UK.

Currently, it is estimated that the death rate owing to swine flu in the UK and the US is 0.5 per cent, which means that about five persons die for every 1000 people infected.

Thus, there is an urgent need for accurate estimates so that health authorities can best target treatment and vaccination strategies.

However, a new analysis has suggested three main reasons why current estimates may be wide of the mark.

The first and main source of uncertainty is the unknown number of infected people, who recover at home without notifying their doctors that they are ill, or receiving a diagnosis.

Thus, despite knowing how many patients are dying of swine flu in hospitals, doctors have no idea about what proportion of all cases are life threatening.

But they need both figures to work out the "case-fatality ratio", which is calculated by dividing the number of fatal cases by the total number of cases.

"We don't know the denominator," New Scientist quited Azra Ghani, head of a team at Imperial College London tracking development of the epidemic in the UK as saying.

"For that reason, dividing the number of deaths by the number of cases may be flawed," said Ghani's colleague Tini Garske, the lead author of the study exposing gaps in the data.

The second piece of uncertainty is the possibility that deaths from swine flu are being attributed falsely to other causes of death, such as heart attacks or pneumonia from other causes.

This would lead to underestimates of the death rate.

And finally, statistics are distorted by a time lag between the point at which someone is infected and the time they die.

This could cause an apparent surge in deaths, which may falsely be interpreted as the virus becoming more deadly through mutation.

Taken together, these factors make it difficult to rely on existing data sources to accurately calculate the death rate or to predict the course of the epidemic.

However, Ghani has said that studies are already planned to rectify these shortcomings.

The study has been published in the British Medical Journal. (ANI)