Abstract: China has consistently attached importance to health work. However, this health work has been limited to the health work in a narrow sense for long and people lack a sense of the public health at large for the whole society. In 1988, Hepatitis A broke out and brought disaster to 300 thousand people in Shanghai. After completing systematic investigations, it was ascertained that this outbreak arose from eating raw clams contaminated by Hepatitis A virus. After prohibiting eating clams and implementing Hepatitis A vaccination over a long period, the incidence rate of Hepatitis A has been reduced to below 1/100 000. The prevention and treatment of Hepatitis A and the control of clams are related to the environment control, aquaculture, commerce, sanitation, epidemic prevention, food safety and other related industries. In the course of controlling the outbreak of Hepatitis A, Shanghai managed to implement the "public health at large". By attaching importance to the "public health at large", Shanghai has strengthened the construction of its public health system, improved citizens'sense of health and promoted the health level for the whole society.