Rubbing alcohol kills them on contact. Quarantine that orchid, spray it liberally with the rubbing alcohol. You can use a Q tip to remove the individual bugs which will turn a dark color once they have alcohol on them. Check the plant closely for a week or 2 repeating the alcohol usage as needed. They like to hide under leaves, in crevasses, on blooms and buds and in/under sheath material etc.
And no, one or two mealy's does not constitute an infestation, but it is good to get it under control as soon as detected.