Obesity has emerged as a possible contributing factor in fatal swine flu cases, according to ground-breaking research looking at deaths caused by the pandemic in countries around the world.
The claim is made by a team from the French Institute for Public Health Surveillance, which has studied the characteristics of 574 deaths associated with the pandemic H1N1 influenza up until the middle of July. According to the team's findings, published in medical journal Eurosurveillance, underlying disease was found in at least half of all fatal cases.
Mortality patterns were in many cases similar to those associated with normal, seasonal flu. But the team observed: "Nevertheless two risk factors are noticeable: pregnancy and obesity."
Pregnancy is already a well-documented risk factor in seasonal influenza and in previous pandemics. The study found that 16 women – representing 10% of all female deaths that were studied – were pregnant or had recently delivered at the time of their death. Half of these also had other health issues.
But the conclusion that obesity may be a factor in some swine flu deaths opens up a new line of investigation for epidemiologists. Where an underlying disease was found to be present after someone had died of swine flu, in more than one in four cases the deceased had a metabolic condition – diabetes and/or obesity.
The team, which concluded further research needed to be done to establish the link between obesity, severe influenza and mortality, also found significant demographic variations among those affected by the pandemic.
"Compared to younger age groups, the elderly seem to be protected from infection to some extent, perhaps due to previous exposure to strains akin to influenza A(H1N1)v virus," the team claim.
There has been a view that fatal cases involving the pandemic have tended to occur among the young, according to the team. And they found the average age of those who have died was 37. More than half of all deaths occurred among the 20- to 49-year-old age group. Overall, 12% of deaths occurred in cases aged 60 years or more.
According to the latest update from the Health Protection Agency (HPA): "In the last seven days, cases reported globally have increased by 8% and the number of deaths by 21%." However, the HPA suggested flu rates in England were now coming down.
Concerns remain, however, that infection rates will start to increase again come the autumn.
The French team warns: "The pandemic… is far from over, and deaths will unfortunately continue to occur. As in previous pandemics, available data show that age groups are not equally affected."
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