Travel insurance policies primarily only provide coverage for any new and unexpected illnesses or injuries that occur after the policy goes into effect. Pre-existing conditions and preventive care are generally not covered due to the short-term nature of these plans. Depending on the age of the insured however, some policies do provide some coverage for an acute onset of a pre-existing condition. An acute onset of a pre-existing condition is defined as a sudden and unexpected recurrence of a pre-existing medical condition and can only be diagnosed by a doctor at the time of visit. That being said, two policies you can consider purchasing for your parents to protect them from anything unexpected is the CoverAmerica Gold plan or the Safe Travels USA Comprehensive plan. These policies can also provide them with some coverage for an acute onset of a pre-existing condition, should anything occur.