No need to be glib Hanaldo. I too have only had 1 flu.
Taps in Public toilets have more viruses/bacteria than in most workplaces > thus use toilet paper. But lots of Public toilets are being designed in such a way as to walk around partitions rather than have to use door handles.
After shaking hands, especially in Flu season, it's common sense to at least wipe that hand on your dacks in a covert way. Uncleanliness Cases in point = teachers getting colds off kids during term; flu pandemic after WWI killed millions; confined areas like aircraft cabins; and lastly, Florence Nightingale had to be a super hardass to get the hospital staff to clean from top to bottom.
It's always laborious if one isn't used to minimising proximity exposure. If its habitual to practise hygiene, not getting a cold or flu is quite easy (unless of course you're in hospital and run the risk of Staph. Aureus or Clostridium Difficile).
Oh yes, one more thing about contagions; Canterbury Rugby League players bombed out the year following a Premiership due to the mildly contagious Glandular fever. They went down like flies.
One doesn't have to be obsessive - just aware.
I've seen loved ones kissing their sick friend/relative in an isolation ward after washing their hands + bringing in indoor pot plants with fertiliser. My immunologist squash friend guessed right > Herpes in the 1st instance and possible Legionnaire's in the 2nd. Well at least they washed their hands lol