You’ll have to be level 25 or higher to participate. The flavor text for this event describes the event as,
“The Hyland Organization for Rakghoul Neutralization (T.H.O.R.N.) has issued an official level-2 emergency alert concerning an outbreak of the Rakghoul plague on Alderaan. Quarantines have been put in place to restrict traffic of the plague off-world, but exceptions will be made for individuals with priority clearance.”
Naturally, you’ll be rewarded for your efforts. Rewards this time include Reputation with THORN, Merciless Seeker’s Armor Set, THORN Epicenter and Dark Vector Armor Sets, Outbreak Response Weapons, Alliance Contact - Doctor Lokin, Infected Varactyl and Infected Dewback Mounts, Ferocious Rakghoul Mini-pets, and more.
A week after the Rakghoul Resurgence event ends, the All Worlds Ultimate Swoop Rally is set to start on July 28 and will run through August 4. Participating in this event will net you Swoop Rally Mounts (regular and gold versions) Swoop Gang Outfits, Promotion Droid Mini-pets, Various Stronghold Decorations, and more.