Researchers have been frantically looking for new and potent antivirals to combat the recent potential epidemics/pandemics of the Swine Flu (H1N1), Avian Flu (H9N2 and H5N1) and others. Chinese Medicinal compounds have shown powerful antiviral effects, so researchers looked into an herb called andrographis that had already exhibited broad spectrum antiviral properties including inhibition of HIV. A compound isolated from andrographis resulted in a 100% survival rate for pandemic H1N1 when administered at the proper time in the proper dose. If you are around sick people, then taking andrographis prophylactically might be prudent. If you think you have the flu, get to an herbalist right away (be sure to wear a mask to minimize the risk of infecting other people). According to this study, if you wait 72 hours after exposure to the flu, this herb and the antiviral drugs have no significant effects.
 
We are recommending the equivalent of about 5g/day for prevention and 10 - 14g for treatment (AE). This herb should be combined with other herbs to mitigate some of the potential side effects according to your particular constitution.
 
Biol Pharm Bull. 2009 Aug;32(8):1385-91