the theory of "four evils" has a long history. On February 12, 1958, the Central Committee of China and the State Council issued the "Instructions on Hygiene in Eliminating Four Pests". The "directive" proposes to complete the task of eliminating flies, mosquitoes, mice and sparrows in 1 years or less. Later, "sparrow" was replaced by "bug", and then "bug" was replaced by "cockroach" It seems that in addition to three of the "four pests", the fourth pest has changed with the change of social life. This morning, the reporter interviewed the Shanghai Center for Disease Control and Prevention, and a staff member clearly told me that the "four pests" should be flies, mosquitoes, mice and cockroaches.