To reduce risk while on-board or in general?
On-board -
Stay at home and don't get on-board
In general -
Wash your hands often and with soap.
Don't touch areas around your mouth, nose and eyes.
If you feel symptoms CALL for medical consultation, don't travel to the clinic as you risk spreading the virus.
Common ways of spreading flu virus is by pushing elevator buttons, touching door handles, shaking hands with people etc etc.
This could become a nasty one and I am pretty certain you will see WHO raising to pandemic level 6 soon.....