Enteroviruses (EVs) are one of the most common human viruses and are a genus of the Picornaviridae family. The main enteroviruses related to human pathogenesis include poliovirus (Poliovirus) types 1-3; Coxsackie virus (Coxsackie virus) A and B groups, group A includes types 1-24 (A23 and Echo virus). Type 9 is the same, so it is actually 23 types); group B includes types 1 to 6; echovirus (Enteric Cytopathogenic Human Orphan virus, ECHO virus) types 1 to 34 (type 10 is reclassified as reovirus 1 Type 28 was reclassified as rhinovirus type 1, and type 34 was reclassified as Coxsackie virus type 24, so there are actually only 31 types). New Enteroviruses isolated after 1969 are uniformly numbered as 68, 69, 70, 71 and 72, of which type 72 is hepatitis A virus, which is now listed as Hepatovirus. In recent years, according to the molecular biological characteristics of the virus, enteroviruses have been divided into five species: poliovirus (PV), including three types of PV1, PV2, and PV3; human enterovirus A (HEV-A) , including CVA 2-8, CVA10, CVA12, CVA14, CVA16, and new enterovirus types EV71, EV76, EV89, EV90, and EV91; human enterovirus B (HEVB), including CVA9, CVB1-6, E1-E7, E9, E11-21, E24-27, E29-33 and new serotypes EV69, EV73, EV74 and EV75; human enterovirus C (HEV-C) including CVA1, CVA11, CVA13, CVA15, CVA17-22 and CVA24 ; Human enterovirus D (HEV-D), including EV68 and EV70. Animal experiments have shown that enteroviruses first infect the epithelial cells of the respiratory tract or intestinal tract, and then invade other tissues, such as the nervous system, myocardium, pancreas, etc., through viremia, resulting in different clinical syndromes such as poliomyelitis, myocarditis, and pericarditis. . Different types of enteroviruses can cause the same clinical syndrome, such as sporadic polio-like paralysis, fulminant meningitis, encephalitis, fever, rash and mild upper respiratory tract infection; and the same type of enterovirus can also Causes several different clinical diseases. Patients, latent infections and asymptomatic virus carriers are the source of infection of the disease, and the fecal-oral route is the main route of transmission of enteroviruses; children are the susceptible population. During the epidemic period of EV infection, the infection rate in children is 10% to 20%, and it can even reach or exceed 50%. Most people infected with enterovirus do not have symptoms, which is a latent infection.

Hepatitis A is caused by the hepatitis A virus. Hepatitis A virus differs from many of the viruses of the genus Enterovirus and has been classified into a new genus, the genus Hepatovirus. After the hepatitis A virus enters the human body through the mouth, it enters the bloodstream through the gastrointestinal tract, causing viremia, and then reaches the liver. The virus can be excreted into the intestine through bile and appear in the feces. The mechanism of hepatitis A virus-induced hepatocyte injury has not been elucidated, but it may be mediated by the body's cellular immune response. Hepatitis A virus infection can be manifested as latent infection, subclinical infection or clinical infection. Clinical infection can be manifested as acute jaundice or acute anicteric hepatitis, and occasionally it can develop into severe hepatitis, but generally does not develop into chronic hepatitis. The main source of infection of hepatitis A is hepatitis A patients or those with latent infection. The main route of transmission of hepatitis A is the fecal-oral route.