This will include pandemic disease such as Influenza A (H1N1)
Most medical card only cover up to 90 days, once you are outside of Malaysia.
Most medical card will only pay amount equivalent to the cost of getting the same treatment in Malaysia. Example: Breaking a leg in US cost USD10K to treat while in Malaysia cost RM10K for the same treatment. The medical card will only reimburse you RM10K. Some insurance company do sell additional rider to pay in foreign currency (USD10K in this example) but of course you will have to higher premium.