Bird Flu: Young at Highest Risk

Influenza often kills the weakest people in society — the elderly and the very young. But bird flu — the H5N1 strain — is acting very peculiar. It’s striking the young — but not the old. And it’s striking those who are near middle age. In fact, 90 percent of cases have hit people under […]

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Influenza often kills the weakest people in society -- the elderly and the very young. But bird flu -- the H5N1 strain -- is acting very peculiar.

It's striking the young -- but not the old. And it's striking those who are near middle age. In fact, 90 percent of cases have hit people under 40.

This could be a sign that a "widespread immunity to infection with the virus may exist in people aged 35 and older."

Why would that be? One possibility that's not discussed in this article: maybe older people developed resistance to a similar strain in the past, but younger people were never exposed to it. (I'm a journalist, not an epidemiologist... If I'm off base here, drop a line in the comments.)

From a news story:

Suggested theories have included that children and young people mayhave closer exposure to poultry in countries where outbreaks areoccurring.

Another possibility could be that older people are actually beinginfected but suffer such mild illness that they don't come to theattention of health authorities.

The few studies that have looked for mildly symptomatic orasymptomatic cases don't support this idea, but experts believe largerstudies need to be done before it could be ruled out.

90% of bird flu cases hit people under age 40: WHO [The Canadian Press, via CBC]