Hi LeeS80 ... that would very much depend on whether the situation escalates and Foreign & Commonwealth Office advice is upgraded.
If for example FCO advice is to avoid large gatherings or non-essential travel to or within certain areas of a country, it is unlikely that any insurance cover would apply if that area can reasonably be avoided, and so alterations or cancellations would be at the discretion and goodwill of the airline or tour operator.
However, if the FCO advised against all travel to a country, then insurance cover kicks in (subject to individual policy terms) and the travel industry begins a programme of repatriation for existing holidaymakers, and alterations, cancellations, etc for future holidaymakers. Situations requiring action such as that are very rare.
David