Oseltamivir is an antiviral medication that belongs to the family of medicines called neuraminidase inhibitors. It is used to treat some types of influenza infection (flu) in adults, children, and infants (older than 2 weeks of age) who have had symptoms of the flu for no longer than 2 days. Oseltamivir is also used to prevent some types of flu in adults and children (older than 1 year of age) when they have spent time with someone who has the flu or when there is a flu outbreak. It helps shorten the time that flu symptoms such as a stuffy or runny nose, sore throat, cough, muscle or joint aches, tiredness, headache, fever, and chills last. Oseltamivir is not a substitute for the flu vaccine. It will not treat colds or infections caused by bacteria or other viruses.