Analysis suggests immunity to bird flu in people over age 35

[Darlene]

This means our children could potentially be at the highest risk.

 

http://dose.canada.com/news/story.html?id=...78-1ca75bb455fb

 

Analysis suggests immunity to bird flu in people over age 35

 

Helen Branswell

 

Published: Saturday, February 10, 2007

 

Nearly 90 per cent of the people who’ve been diagnosed so far with H5N1 avian flu were under age 40, a new analysis from the World Health Organization shows.

 

And two British scientists suggest that as yet unexplained phenomenon could be a clue that widespread immunity to infection with this virus may exist in people aged 35 and older.

 

In a letter to the March issue of the journal Emerging Infectious Diseases, Matthew Smallman-Raynor of the University of Nottingham and Andrew Cliff of the University of Cambridge note that the age distribution of H5N1 human cases is "consistent with a biological model of geographically widespread immunity to avian influenza A (H5N1) in persons born before 1969."

 

"Such a model would account for the similar rates of disease activity in younger age categories, the sudden and pronounced reduction of cases in patients over 30-35 years of age, and the age skew that transcends the sociocultural and demographic contexts of countries and continents,” wrote Smallman-Raylor and Cliff, who teach analytical and theoretical geography respectively.

 

It is not known why H5N1 seems to prefer the young and rarely infects the elderly, the age group hardest hit by seasonal flu.

 

Suggested theories have included that children and young people may have closer exposure to poultry in countries where outbreaks are occurring.

 

Another possibility could be that older people are actually being infected but suffer such mild illness that they don’t come to the attention of health authorities. The few studies that have looked for mildly symptomatic or asymptomatic cases don’t support this idea, but experts believe larger studies need to be done before it could be ruled out.

 

The two British scientists looked at ages of reported cases and compared them to population figures for countries reporting human infections, looking to see if the demographic compositions of those countries provide some clues.

 

Their analysis showed that the imbalanced distribution of cases is seen in both genders, throughout the duration of the ongoing H5N1 outbreak (which began in late 2003) and across all countries which have had enough human cases so that statistics could be crunched.

 

That suggests that the trend probably isn’t due to local cultural or geographic factors, argued Smallman-Raynor and Cliff, who said the idea needs further study.

 

"If an element of immunity to avian influenza A (H5N1) does exist in older populations, its possible association with geographically widespread (intercontinental) influenza A events before the late 1960s merits further investigation,” they said.

 

The WHO analysis, published in the agency’s online journal the Weekly Epidemiological Review, also argues that the higher proportion of cases in younger age groups probably isn’t just due to the fact that young people make up a big part of the age structures of affected countries.

 

The report, which covers the 256 laboratory confirmed cases that occurred between Nov. 25, 2003 and Nov. 24, 2006, showed that the median age of cases was 18 years old.

 

Fifty-two per cent of cases were younger than 20 years old and 89 per cent were under age 40. Men and women made up virtually an equal number of cases.

 

The death rate was highest among cases aged 10 to 19; 76 per cent of cases in that group died. Cases aged 50 and over had the lowest death rate (40 per cent) followed by children under age five (44 per cent) and children aged five to nine (49 per cent).

 

The total case fatality rate was 60 per cent.

 

Cases have increased over time, the unnamed authors reported, with the cases in the second year of the three-year period twice as high as those recorded in the first year. From year 2 to year 3, the number of cases rose by about 25 per cent.

 

A graph of cases showed that while there are definitely seasonal peaks and troughs in human infections, there have been cases recorded every month since November 2004.

[Lois]

This is enough to make you want to hibernate with your kids.

[Mother]

I had already noticed the general age of people getting the flu some months back but it's my feeling that the immunity might be only for people in those areas where they live daily with poultry. Most of those areas are warm climates where poultry is either home raised, mostly running free, or sold live and butchered either on the spot while the customer waits or at home. It's possible that older people contracted a milder strain of the disease and now it's mutated quickly enough that the younger ones are suseptible to it. I understand the drug companies originally started to try to find a vaccine using the 2003 strain but have since moved on to the newer one, which, by the way, Indonesia does NOT want to give away FREE. It wants to SELL it!!!!!!

 

I suppose the strain of the 1950's and 60's flu could give ammunity but I thought that was a totally different strain as they weren't using those types for vaccines against the bird flu.

 

I for one am not holding my breath. Migration seasons will be starting again in the spring but that should be from south to north and I'm hoping we're home free until at least fall again but it only takes one illegal bird brought into a country to bring the disease. Take my word for it, illegal poultry is a BIG business whether it's for fighting roosters or just for the gene pool and collection value of rare birds.

 

We have as much control over our poultry here as the UK does. What does that tell you? That we can only hope it can be stopped within birds. I'm still more worried about that one last mutation that makes it go H to H. Then we will see it migrate here the easy way, via airplanes.

[Snowmom]

Here is a map of where the bird flu in people is located.

 

http://news.bbc.co.uk/1/hi/in_depth/world/...flu/default.stm

 

I know that even the other flu is taking lives. There have been at least 4 children and one adult in MN who have died of flu this winter. One of the children had had the shot. I'm not sure but I think the child had other complications too, I mean this child had other medical problems.

 

They are saying that everyone should have the shot now.