The entire population was wiped out by the Goa'uld Nirrti when she released a Engineered Virus into the planet's water and ground.
As a result, everyone died, including Stargate Command team SG-7, leaving a young twelve-year-old girl named Cassandra as the only survivor. SG-1 brought her back through the Stargate and Cassandra nicknamed "Cassie" now lives on Earth.
Four years later, SG-1 returned to save Cassandra, finding that the bacteria had died off and that the planet was once again safe. (SG1: "Singularity", "Rite of Passage")
A large sign is on display near the Stargate which announces "Welcome to Hanka" and bears the symbol of SG-7. It identifies the presence of the "Douglas Mclean Memorial Observatory" and names SG-7's late commander as "John Smith".