Post Reply - Cambodia 8th H5N1 case

while several had mild symptoms

   https://afludiary.blogspot.com/2024/08/cambodia-reports-8th-h5n1-case-of-2024.html or https://afludiary.blogspot.com/2024/08/cambodia-reports-8th-h5n1-case-of-2024.html ;
For the third time in the month of July, and the 14th case over the past 18 months, Cambodia's Ministry of Health is reporting a new H5N1 case, this time in a 4 y.o. boy from Svay Rieng Province. 
All of the cases reported in Cambodia to date have been from an older 2.3.2.1c clade of H5N1, which predates the emergence of clade 2.3.4.4b which has spread across much of the rest of the world.
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The boy had a fever, a cough, tiredness, difficulty breathing and drowsiness. At present, the patient's condition has improved and he is receiving intensive care by doctors. 
According to the interrogation, about 12 days before the onset of illness in the village and at home, the patient had a large number of dead chickens and flowed and brought food to eat, the boy touched and held the dead chickens and liked to play With chicken and duck.
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Of the 14 H5N1 cases reported by Cambodia over the past 18 months, only 3 have been in adults and all of them survived.  Among the 11 children infected - while several had mild symptoms - nearly half (n=5) have died. 

We've seen this affinity of H5N1 to preferentially infect younger people often over the years, although the reasons behind it are poorly understood. 
One possibility we've explored, however, is that your first flu exposure may affect your future response to novel flu viruses (see Science: Protection Against Novel Flu Subtypes Via Childhood HA Imprinting).
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 H5 is an HA Group type 1 while H7 viruses fall in group 2.
Those born prior to the mid-1960s were almost certainly first exposed to Group 1 flu viruses (H1N1 or H2N2)
Those born after 1968 and before 1977 would have been exposed to Group 2 (H3N2)
After 1977, both Group 1 and 2 viruses co-circulated, meaning the first exposure could have been to either one.
This suggests that those born before 1968 may carry some degree of limited protection against H5 infection. 

That said, any advantage of being born in the 1950s or early 1960s is probably being gradually offset by advancing age and comorbidities, and may not be as pronounced today as it was 20 years ago.

Today's report is a reminder that while we are heavily focused on clade 2.3.4.4b of H5N1, there are a number of other novel flu viruses with zoonotic potential that have pandemic potential, and deserve our attention.
DJ, Being exposed to flu types earlier may -for now- offer -limited- protection against new types of flu...

The further in time the more mutations and that means LESS immunity...