Dear Bhavanikumarm,
Extra marital affairs, as long as they do not interfere with the functioning or the general environment of the workplace, is the private matter of the parties themselves. The office or employees have no matter interfering in it.
-But, the minute it starts interfering or causing disturbance to co-workers or to the general functioning of the workplace, they should be given a warning or a feeler. It is not advisable to mention it as the "affair", but as their general disposition (behaviour)or "what people have mentioned to the HR concerned".
-When there is public display, any event or general misfeeling about the affair ( like in the article in the original post), there should be a talk.
* Have a talk with them or ask their closest friend to mention that there is some talk about it in the workplace
* Counsel and mention to them that personal matters are better kept personal and out of business boundaries
* If it is leading to dirty linen being washed in public (spats, arguments or unacceptable things), have the seniormost authorityin the HR or their own dept talk to them about it being unethical
*Other measures if they reciprocate and ask for help-Psychiatric help(tell them they do not treat only sick people!); across the table session with both them and reach a consensus;transfer
Circumstances and problems;desire for treading the forbidden path drive deviant behaviour.
Affairs are sensitive matters as they are doing something beyond the social boundaries. it has to be dealt with carefully.