I'm a fan of the Sawyer PointZeroTwo Purifier
. With its .02 Micron absolute hollow fiber membrane purifier, it filters bacteria, cysts, and yes, even viruses. They have a cheaper PointOne model (.1 Micron) that does not claim to filter out viruses.
As for any filter claiming to be "the only EPA approved filter," consider that according to the CDC
the EPA does not approve or test filters. If someone is willing to mislead you about such a thing, what else are they misleading you about? Three organizations do test water purification systems and certify if they meet or exceed ANSI/NSF or EPA standards: NSF International, Underwriters Laboratory, and the Water Quality Association.
P.O. Box 130140
Ann Arbor, MI 48113-0140
877-8-NSF-HELP; (877) 867-3435
Underwriter’s Laboratories, Inc.
333 Pfingsten Road
Northbrook, IN 60062-2096
Water Quality Association
4151 Naperville Road
Lisle, IL 60632-3696