love-affair（回答）

love-affairには「情事」以外に「（ものに）夢中になること，大好きなこと，熱狂」という意味がります。日本人としては好きで夢中になっているわけではないと思いますが，異文化の視点からはそのように見えるのでしょう。love-affairを副詞的に捉えて「日本人が熱心にうがいをしている一方で」と解釈してみました。（Koyamamoto）

Despite Japan's love-affair with gargling and the consequent potential for bias, these studies seem to have a solid, logical setup: In all the ones I read, individuals had been randomly assigned to either a non-gargling control group or a gargling test group. The experiment ran for a few months like this, and at the end researchers tried to find out which group had caught the most colds during the experiment. Some studies included iodine mixes among their test groups; other studies tried to calculate the cost-effectiveness of gargling as preventative care.
http://www.accessj.com/2012/12/ugai-japanese-people-love-gargling.html