Sadly there is a lot of misleading information around on this subject at the moment, notably a report stating that 97% of all viruses etc are on Android, but usually the report is only partly quoted, especially by Android's competitors. Technically the figure may be true but it does NOT relate to the official Android app provider, Google's Play Store. A mere 0.01% of the problem apps affect the Play Store and even these are removed quickly and only affect phones that have not had the latest OS updates applied.
The risky applications come from unapproved app stores, mainly from Russia, China and similar places and are usually found in pirated games. All Android phones are programmed to restrict the user to only download applications from the official Play Store, but the user can ignore the prominent on-screen warnings and manually override this setting if they choose. Those who do have no one else to blame but themselves if they pick up a virus or malware of some sort.
Since 87% of phones internationally use the Android OS, it is no wonder that the scanners focus their attention on Android phones. Users however are quite safe if they use the official Play Store for any apps they want and make sure they keep their phone software up to date.