With the help of Zhang, Apaio graduated with the master degree and became the first oral surgeon of PNG.

In 2015, Zhang was assigned to join the medical aid in PNG for the second time. Because of the experience before, Zhang was named the captain of the seventh Chinese medical team to PNG.

"It was not easy for me, for all kinds of critical conditions in PNG and teammates having difficulties in adapting, so I was under a lot of pressure unprecedentedly," Zhang said, "the most unexpected is dengue viruses, which used to be far away from us in China but were hidden closely around us here. "

PNG is the epidemic area of AIDS, tuberculosis, malaria, dengue fever and typhoid. Different types of dengue virus cross spread, resulting in surprisingly high morbidity of dengue fever in PNG.

Although the medical team took a lot of preventive measure, they still got caught by the disease. On May 6th, 2016, He Shengjiang, the vice-captain of the medical team and an orthopedic expert, was infected with dengue fever; on the same day, Deng Hongbin, a medical oncologist, was infected as well; by 20:00, Zhang also showed the symptoms of infection.

At this point, the medical team was scared, asking for Zhang's instruction for the next step. "Healthy ones continue working. Sick ones, we take care of each other!" Zhang made a rigid requirement immediately.

"I still remember that there were 18 steps from the first floor to the second floor in our station. I didn't pay attention before, but when I was sick, every step was every difficult for me," said Zhang. Suffering from high fever, Zhang had to go upstairs slowly to infuse for sick ones.

Zhang fought against dengue fever with his teammates for nearly 3 weeks. Sick ones infused medicine and got drugs for each other. They finally overcame it.

Among the ten-member medical team, seven were infected with dengue fever, and three who hadn't been infected were insisting on providing medical services at the hospital.

"This experience made me feel that in PNG, we were surrounded by dangers. As the captain, I need to protect my teammates more," Zhang said, "PNG is the place full of my memories, and foreign aid is the thing that I'll be proud of for my whole life!"