Eupatorium is used for Influenza in acute homeopathic care.
It has such a distinctive picture that once you see it, the choice of remedy is clear.
In any kind of fever or influenza the sufferer will feel severe aching pains all over, as if their bones were broken (hence the name of this plant is Boneset). All parts of them feel sore and painful (even their eyes!).
Although it is important to compare this with Bryonia it is the all over painfulness during influenza (as if the bones had broken) that will guide you to this remedy.
Severe aching and pains during influenza and fever
Influenza
Fever