About the 'real bird flu', the H5N1 strain. This is a flu disease that has come from Asia and has spead to Europe. This flu spreads from bird to bird, but can also infect other species, including humans. But it cannot spread from human to human. About 205 people have catched this H5N1 strain and 113 people have died. Most of these people died in 2004 and 2005 in Vietnam. Four people died this year in Turkey.

Now this is nothing new. Bird flu is known to be able to inflect and kill people in rare cases. But this is the dangerous part for developing a new human flu virus that can cause a pandemic. If a human is inflect with both a human flu and a bird flu they may intermix more easily and a totally new human flu, based on the bird flu genes, will develop.
This bird flu seems to have lost steam. It spead accross Europe but has not killed a single human. It does not seem that this virus will mutate into a human variant. Something that was feared a few years ago and started the whole thing. Maybe if the wild birds are done breeding the virus will become more active. Maybe we will have to wait until a new bird flu develops and see it is will spread to humans. The chance is small. But if it happens, and it does happen, it can kill 5 to 150 million.
So there is a chance that there will be a human flu, probably based on the genetics of the bird flu, that can kill a lot of people because it is a totally new strain of flu. This happened a few times the last century.
The big example, in 1918-1919 50 million to 100 million people died because of the 'Spanish flu'.
Now the Spanish flu is supposed to have come from birds. It mutated, or evolved, so it became a human flu virus. And then it is just like a normal virus, except that our body cannot fight it. At least not at first, before a lot of people die.
And yes, you can't really do anything about it. First of, any medicine that might help will be in too short a quantity. Of course it depends on how large the pandemic may be. It could be only 10 million dead world wild. But even then everyone in the world will want to get the medicine. You will have only one weapon, your own immune system.
And about the medicine that area available. A flu shot, which seems to be common in the US but is only used on the elderly where I live, only works for a particular strain of flu. Because the flu virus evolves very fast a new strain develops every time. So even the flu shot from last year is on nu use for the new flu strain of tomorrow. Let alone a flu virus that is largely alien to us because of the bird flu genes.
If this new dangerous flu virus shows up people immediately want to develop a vaccine for it. It is a very weak variation of the virus that learns our immune system how to fight the real virus. So our body will learn to produce antibodies that destroy the real flu virus.
To devep a vaccine will take some time. And when the virus becomes a pandemic everyone will want one. Look at the Spanish flu, it only needed two years to spead around the world. That was in an age without airplanes. In your world it can spear very very quickly. It could spear around the whole world before a 100 people have died from it.
And then you have 'virus slowers' (no idea how they are called in english). They try to slow down any virus in your body. I am not sure how effective these will be. They do not cure you. They do give your body more time to develop antibodies to kill the virus. I am not sure if they would work at all. The virus slower could be entirely too slow itself. Again, if people all over the world are ill everyone will want them, even if they don't actuallly help in most cases.
As for the 'bird flu pill', no idea what it is. Must be a 'virus slower' but the name is totally deceptive.
Let me also point out that it is not certain that 100 million peole will die in the next 20 years. There could be a new virus outbreak tomorrow. It may kill 10,000 in Asia or it may kill 150 million all over the world. Maybe the next pandemic will only be in 2106. Maybe, maybe even probably, not.
And when the bird flu happens. I guess one would hope a vaccine is developed before the virus reaches Europe. The virus will probably originate from Asia because of the large number of chickens and other birds kept there. I guess Northern America will be safer. But you never know. SARS reached Canada but not Europe, if I remember correctly. With planes everything can happen. If not then you have to trust in your immune system. I guess you will have to pray to god.