This paper introduces the background of novel coronavirus's adjustment from "Class A tube" to "Class B tube", especially the important achievements and experience of epidemic prevention and control in recent three years, the current virus characteristics, epidemic situation, vaccination and medical resources preparation, which fully explains the scientific and necessary implementation of "Class B tube".

(2) Preparation measures.

Focus on training vaccination, drug reserves, medical resources preparation, graded diagnosis and treatment and other measures, all localities and departments can highlight the training focus according to the actual situation of the local and industry.

(3) Prevention and control measures.

Focus on training the adjustment of prevention and control measures after the implementation of "B and B management" in novel coronavirus, including the basis of detection strategy adjustment, epidemic monitoring, publicity and guidance, prevention and control measures for key populations, key institutions and key places, etc.

According to the outbreak, epidemic situation and harm of infectious diseases, legal infectious diseases in China are divided into three categories: A, B and C.

1.？ Class A infectious diseases are also called compulsory management infectious diseases, including plague and cholera.

2.？ Class B infectious diseases, also known as strictly managed infectious diseases, include COVID-19, SARS, avian influenza, influenza A (H 1N 1), viral hepatitis, measles, whooping cough, tuberculosis, rabies, polio, Japanese encephalitis, malaria and AIDS.

3.？ Class C infectious diseases are also called monitoring and management infectious diseases, including influenza, mumps, hand, foot and mouth disease and so on.