When her refit was completed in March 1917, "Africa" was attached to the 9th Cruiser Squadron for service in the Atlantic Patrol and for convoy escort duties. She was based mainly at Sierra Leone and escorted convoys between Sierra Leone and Cape Town, South Africa. She underwent a refit at Rio de Janeiro, Brazil, from December 1917 to January 1918. In September 1918, while "Africa" was based at Sierra Leone, some of her crew became ill during the influenza pandemic that broke out that year. Their numbers virtually doubled each day from less than a handful at the start of the month until 9 September, when 476 crew members were reported ill. On that day, one crewman was reported dead of pneumonia following a case of influenza. Five more crewmen died on 12 September. The next day, another eight perished. On 14 September, ten more crewmen died. "Africa" sent burial parties ashore daily, and the ship was put into quarantine. By the time "Africa" hauled down her quarantine flag on 30 September 1918, 52 crew members had died of illness out of a total complement of less than 800.