There has been much talk about Tamiflu and the possibility that it can curb the reproduction of the H5N1 virus.  Tamiflu works by inhibiting an enzyme called neuraminidase (aka sialidase).  This enzyme is used by many virus particles to attach to cells and invade them.  When a neuraminidase inhibitor like Tamiflu is administered, it can reduce the spread of Type A influenza in the population.  It can also shorten the duration and intensity of Type A influenza if administered in the first 48 hours after symptoms appear (it typically reduces a 5-7 day influenza episode by 1 to 2 days).

The strategic use of neuraminidase inhibitors can probably help keep a lid on small outbreaks of the virus.  But if a larger epidemic occurs, supplies will probably run short.  Viruses have demonstrated the ability to mutate and become resistant to Tamiflu, which could be a problem over time.

There are natural neuramidase inhibitors found in plants: the most widely studied is a compound called 5,7,4'-trihydroxy-8-methoxyflavone, which is found in the herb Scutellaria (commonly called scullcap or skullcap).  In a study on mice cells, bathing the cell cultures in Scutellaria tea inhibited both Type A (H3N2 type) and Type B (Ibaraki/2/85 type) influenza when the flavone was administered 18 hours before the virus challenge.  (it significantly inhibited their proliferation in the mouse lung when administered intranasally 7 times (total 3.5 mg/kg) from 18 h before to 54 h after virus infection.
 (citation)