Answer:
They did not try to do this.
Bird flu, when it first crossed over to humans, was not human to human transmissible.
But as a virus evolves, we expect sooner or later that it would get that ability.
Researchers do not need to try to get evolution what evolution would do all by itself anyway.
I know that very often the people that say that the Chinese created a virus in a lab are also people that say that they do not believe in evolution.
Stop being a hypocrite about it.
No one was researching how to do this, no one needed to research how to do this because this is done naturally by natural evolution, and no one would want to do this for any reason.
When you accuse “researchers” of trying to do something that has no benefit to science then you accuse all science researchers when you lie about it.