How do flu shot developers know which strain is going around before it goes around?

It is my understanding that a new flu shot is needed each year because the virus evolves and new strains emerge. How does the CDC (or whomever it is that develops the yearly flu shot) go about identifying those new strains before the flu season rolls around?

They look to China and Southeast Asia where most of these viruses come from. In those countries people and livestock live in the same house so when an existing flu virus in an animal mutates it can jump the species barrier and suddenly become dangerous to humans. This is why the bird flu was so dangerous. It was first discovered among birds and it was a very tough germ and hard to kill. If it had jumped the species barrier then we could have had a pandemic like the flu in 1918.

Antibiotics don't help at all against a virus like the flu. Flu work by having a strain of flu incubated outside a host, typically in eggs. The virus is killed and then it is injected into the person. Their bodies antibodies recognize the virus and develop antibodies against it. With Bird Flu this is very difficult for the birds to do and it would probably be just as difficult for humans.

It is important to get your flu vaccination early in the flu season because once you already have the flu introducing more flu virus (even dead virus) won't help you that much.

they quess

Dice?

Each vaccine contains three influenza viruses-one A (H3N2) virus, one A (H1N1) virus, and one B virus. The viruses in the vaccine change each year based on international surveillance and scientists' estimations about which types and strains of viruses will circulate in a given year.

They just have to quess

It is my understanding they watch what is happening in China and this is generally where it all comes from. The winds blow the flu along with travelers and then it passes around the world.

They don't. The current year's flu vaccine is from the previous year's stain and the most likely stains to appear. The worst flu ever got was gotten even though I got the flu shot. I still get it every year since I work in healthcare. But the vaccine won't protect you 100%.

Most flu strains originate in China. The scientists study the strains from the previous years to make new vaccines for the following years. This must be done on a constant basis as the strains are always adapting and vaccines become obsolete.

We studied this in college microbiology and physiology. I can't remember much more but there is something to do with animals in China and conditions there being so fruitful for influenza.

Getting some interesting answers...