New Delhi, July 23 -- The Ebola outbreak in eastern Congo is now the fastest-growing one in history with over 1,000 people dead, and new challenges are emerging in containing a type of the virus with no approved treatment or vaccine.

Strikes by unpaid workers at health centers at the heart of the outbreak could light the flame for others in a remote region already suffering from bare-bones infrastructure, rebel threats and misinformation asserting that the deadly virus isn't real.

The director-general of the Africa Centers for Disease Control and Prevention, Dr. Jean Kaseya, said Wednesday that 1,031 deaths have been confirmed. The outbreak is mostly concentrated in remote Ituri province, which accounts for nearly 90% of cases, but case...