A feature of most of Avast programs is their capacity to update themselves directly. If you are connected to the internet, virus database updates files are downloaded and installed directly without any user activity. The availability of a new database version is inspected when an internet connection is settled, and every four hours subsequently. If you computer does not have an internet connection you can use the offline update method.
Avast! software is able to update its virus definitions database automatically, as long as an active Internet is available. The program checks every four hours if a new database update is available. If your computer does not have an Internet connection, you can download the offline database updates from this page. The virus definitions database is updated daily.
Please note that is not necessary to reinstall the program in order to update the virus definitions database.