(b)Clause (a) is not to be read as prohibiting the treatment as casual leave of absence from duty following on leave granted under the rules, so long as such absence is due to reasons involving no evasion of the rules in regard to the matters above specified, as, for instance, when it is necessitated by-(i)detention in plague camps on the way to rejoin; or(ii)orders not to attend office in consequence of the presence of infectious disease in the family or household of the person concerned.