H7 is not currently a threat to humans. But it has an amazing mechanism, so that if it did, it could really become a “Satan Bug”. H5 has something like it that makes it extra lethal, but it is far less complex than H7.
So if we can figure out H7, we will be well on the way to figuring out H5. It’s a lot safer to mess with H7, because there is little danger of it escaping and attacking humans.
In case you are interested, there are at least 16 known variants of “H” and 137 known variants of “N”. Simply put, the “H” factor is how viruses get into cells, and the “N” factor is how they get out again, so they can infect other cells.
The first three “H” types (H1, H2, H3) and H5, which is new, are found in humans. N1, N2, N3, and N7 are the known human “N” types, but only N1 and N2 have ever caused epidemics.
To make matters more complicated, Influenzas are also subdivided into types. Type A flus affect birds, humans and some mammals, especially pigs. It is the type of flu that mutates most frequently. Type B flus affect humans and, of all things, seals. It mutates more slowly. Then there are Type C flus, that only mutate rarely and generally are very mild.
When vaccines are prepared each year, it is based on the estimate of the two most likely A type flus, and the most likely B type flu. And yes, it is guessing. But importantly, even if they don’t guess the exact strain, the vaccine can sometimes lend partial protection. This means that it makes it harder to get infected, less severe, and that your immune system responds faster.
But within a flu type and strain, there is still a LOT of room left for variation. Influenza has an incredible number of what are called “flexible” genes, that are unstable and very prone to mutation.
To put this in perspective, Vietnam’s chief epidemiologist discovered a herd of swine, each of whom had about five distinct subtypes of the same strain of flu in them, fighting it out in “quarterfinals”, with one subtype emerging as the “best” flu in that pig. At the same time they were fighting with each other, they were also fighting against the pig’s immune system, the “super heavyweight fighter.”
Then their champion would fight with other pigs champion subtype, in “semifinals”, until the grand champion flu strain had defeated all challengers and become the winning strain, infecting all the pigs in the herd.
He noted that it was like a computer algorithm, and that countless other herds of mammals and flocks of birds were doing the same “computation”, to develop the best, all-around strain of influenza.
For this reason, when classifying strain subtypes of flus, they try to establish the lineage of the flu, what flu it is descended from. They also list where it was found, in what animal it was found, a number assigned to it as a unique classification, and sometimes whether it is low pathogenic (LPAI), or high pathogenic (HPAI), which means how deadly it is.
So the full name of a flu might be:
A/Burbank/Chicken/207/2004(H3N2)(LPAI). Type A, found in Burbank in a chicken, the 207th known subtype, in 2004, of the type H3N2, low pathogenic.
Thanks for the exposition, I appreciate it since I’ve followed and been concerned by H5N1 for some time.
Some of that info I knew, much of it was new to me, again, I thank you.