Is there such thing called an ef5 hurricane?

No. EF5 is a rating used for tornadoes, not hurricanes. Tornadoes in the United States and, as of 2013, Canada are rated on the Enhanced Fujita scale, with ratings from EF0 to EF5. EF5 is the highest and rarest intensity rating.

Hurricanes are rated on a different scale, called the Saffir-Simpson scale, which ranges from category 1 to category 5, with 5 being the highest and rarest rating as well.