To provide a peanut testa extract which is safe and effectively suppresses influenza virus; to provide a peanut testa extract, a grape seed extract and an adzuki bean extract, all being safe and effectively suppressing swine-derived A/H1N1 new-type influenza virus; to provide an adzuki bean extract for effectively suppressing Tamiful-resistant influenza virus; and to provide a food composition or a feed composition, both useful for suppressing influenza virus, swine-derived A/H1N1 new-type influenza virus or Tamiful-resistant influenza virus.

A method for improving or preventing a clinical state induced by influenza virus is provided by using a peanut testa extract as the effective component. A method for improving or preventing a clinical state induced by swine-derived A/H1N1 new-type influenza virus is provided by using at least one selected from among a peanut testa extract, a grape seed extract and an adzuki bean extract as the effective component. And a method for improving or preventing a clinical state induced by Tamiful-resistant influenza virus is provided by using an adzuki bean extract as the effective component.