Investigations are ongoing to determine the source of the infection and whether additional people have been infected with swine influenza viruses.
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| Swine Flu Antiviral Drugs
There are four influenza antiviral drugs approved for use in the United States (oseltamivir, zanamivir, amantadine and rimantadine). The swine influenza A (H1N1) viruses that have been detected in humans in the United States and Mexico are resistant to amantadine and rimantadine so these drugs will not work against these swine influenza viruses. Laboratory testing on these swine influenza A (H1N1) viruses so far indicate that they are susceptible (sensitive) to oseltamivir and zanamivir.
Benefits of Antiviral Drugs
Treatment: If you get sick, antiviral drugs can make your illness milder and make you feel better faster. They may also prevent serious influenza complications. For 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. |
Prevention: 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 swine 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.
CDC Recommendation
CDC recommends the use of oseltamivir or zanamivir for the treatment and/or prevention of infection with swine influenza viruses.
- Oseltamivir (brand name Tamiflu ®) is approved to both treat and prevent influenza A and B virus infection in people one year of age and older.
- Zanamivir (brand name Relenza ®) is approved to treat influenza A and B virus infection in people 7 years and older and to prevent influenza A and B virus infection in people 5 years and older.
Recommendations for using antiviral drugs for treatment or prevention of swine influenza will change as we learn more about this new virus.
Antiviral Resistance
This swine influenza A (H1N1) virus is sensitive (susceptible) to the neuraminidase inhibitor antiviral medications zanamivir and oseltamivir. It is resistant to the adamantane antiviral medications amantadine and rimantadine.
Seasonal influenza A and B viruses continue to circulate at low levels in the U.S. and in Mexico. Currently circulating human influenza A (H1N1) viruses are resistant to oseltamivir and sensitive (susceptible) to zanamivir, amantadine and rimantadine. Currently circulating human influenza A (H3N2) viruses are resistant to amantadine and rimantadine, but sensitive (susceptible) to oseltamivir and zanamivir. Therefore, at this time antiviral treatment recommendations for suspected cases of swine influenza A (H1N1) virus infection need to consider potential infection with swine influenza A (H1N1) virus as well as human influenza viruses, and their different antiviral susceptibilities.
Antiviral Treatment
Suspected Cases
Empiric antiviral treatment is recommended for any ill person suspected to have swine influenza A (H1N1) virus infection. Antiviral treatment with either zanamivir alone or with a combination of oseltamivir and either amantadine or rimantadine should be initiated as soon as possible after the onset of symptoms. Recommended duration of treatment is five days. Recommendations for use of antivirals may change as data on antiviral susceptibilities become available. Antiviral doses and schedules recommended for treatment of swine influenza A (H1N1) virus infection are the same as those recommended for seasonal influenza. | 
