Pediatric cases of H7N9 - why are they doing so well?

[Laidback Al]

Pediatric cases of H7N9, why are they doing so well?

So far there have been four reported pediatric cases of H7N9, all younger than 7 (see list below with FluTrackers Case Numbers).

#14 4-year-old boy ? recovered. (Shanghai)

http://www.flutrackers.com/forum/showthread.php?t=203202

#44 7-year-old girl ? hospitalized. (Beijing)

http://www.flutrackers.com/forum/showthread.php?t=203835

#61 4-year-old boy ? neighbor of the 7-year-old girl ? asymptomatic. (Beijing)

http://www.flutrackers.com/forum/showthread.php?p=492876#post492876

#78 2-year-old boy ? recovered. (Shanghai)

http://www.flutrackers.com/forum/showpost.php?p=493264&postcount=3

This is a really small sample size, but with the exception of the one hospitalized girl, they are doing remarkably well compared to the high fatality rate and extensively hospitalized older infected individuals.

Can we speculate on cross-protective immunity from circulating influenza viruses? Or is it something else, perhaps that the developing immunological response of children simply sees all influenza infections as novel and adjusts accordingly. It is worth remembering that in 2009 numerous children in Egypt contracted H5N1 but had only mild infections and most recovered.
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[Giuseppe]

Re: Pediatric cases of H7N9 - why are they doing so well?

This is of Paramount importance.

The host response is almost important as pathogen virulence in some cases.

Young individuals have likely a Abs repertoire less wide than older people.

If one considers the 'immune original sin', and the expected higher response in the elderly toward old antigens rather than newest, it would be interesting to see whether children may Mount an heterotypic response more effective.

The distribution of cells with affinity with H7N9 HA may also be variable between the two classes of age.

Children play also a lot with domesticated birds. Is this behaviour at the base of a some degree of immunity toward H5/H7 viruses than older people?

H1pdm09 infections in older people may have caused a higher response toward old H1 strains and less heterotypic response?

[curiosity]

Re: Pediatric cases of H7N9 - why are they doing so well?

Their respiratory systems are, after all, closer to the ground - aka the chicken.
Not to mention their hands are never clean, and they'll eat just about anything off the ground (excluding many vegetables.)

[alert]

Re: Pediatric cases of H7N9 - why are they doing so well?

Don't also exclude the possibility that milder pediatric cases are being detected because testing requirement might be more stringent in children (as a SARI case in a child is more unusual than in an adult, and also to prevent spread in schools), so mild cases in children might be detected that are being missed in adults.