If you get sick, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious influenza complications. In treatment, antiviral drugs work best if started as soon after getting sick as possible, and might not work if started more than 48 hours after illness starts.

Influenza antiviral drugs also can be used to prevent influenza when they are given to a person who is not ill but who has been or may be near a person with H1N1 influenza. When used to prevent the flu, antiviral drugs are about 70% to 90% effective. When used for prevention, the number of days that they should be used will vary depending on a person's particular situation.

There are four different antiviral drugs that are licensed for use in the U.S. for the treatment of influenza. At this time, CDC recommends the use of oseltamivir (brand name Tamiflu ®) or zanamivir (brand name Relenza ®) for the treatment and/or prevention of infection with H1N1 influenza viruses. The other two antivirals, amantadine and rimantadine, are ineffective for treating the most recent H1N1 flu viruses in humans.