Antiviral medications do not prevent infection, but they can be very effective at decreasing the severity of the symptoms when the flu is caught, and shortening the time period for the body to get rid of the virus.
The Centers for Disease Control and Prevention (CDC) information says that the swine flu can be treated, if caught very early, with two of the anti-viral medications: oseltamivir (Tamiflu/Fluvir) and zanamivir (Relenza). Tamiflu is for treatment in adults and children aged 1 year and older, and must be taken within 48 hours of the first symptom.
Talk to a health care professional to find out if it is an appropriate medication for the treatment of the person involved. (If the person is a child, ask about side effects that have been being seen in some children treated with Tamiflu.)