My first go to for the acute onset of any cold or flu is homeopathy. Homeopathy is a simple, safe and effective way to treat most common acute ailments. I recommend everyone invest in a basic homeopathic first aid kit. When its 2am and you or your loved one is in the midst of an acute illness, you will be glad you have your kit on hand.
Early on it may not be possible to distinguish between a cold or flu. In that case, base the choice of remedies on your symptoms. Most of the following are from the Banerji Protocols and work quickly and effectively when you nip the symptoms in the bud at the first sign of onset.
Onset of generalized cough and cold, often with fever - Aconite 200 with Bryonia 30
Onset of generalized fever - Eupatorium 30 with Belladonna 3
Onset of fever/flu where chills and an icy cold feeling predominates - Camphora 30
Onset of fever/flu where bone pains predominate - Eupatorium perf 30
Onset of cold or flu where sneezing predominates - Arsenicum album 30
Sore throat predominates - Hepar sulph 30
Fever associated with Influenza - Bryonia 30 with Rhus tox 30
The dose is 2 pellets every three hours or as needed for symptoms. If there are two remedies listed, the dose is 2 pellets of each every three hours. The frequency in dosing of homeopathic remedies is reduced as symptoms improve.