Kissing a child on the mouth may transmit herpes viruses, viruses transmitted by the fecal-oral route, and viruses of the respiratory system to the child. 1. Herpes virus: If an adult is in the rash stage of herpes virus, he/she may transmit herpes virus to a child. 2. Viruses transmitted by fecal-oral route: These include norovirus, Helicobacter pylori, poliovirus, and coxsackie virus, which may be transmitted to a child when kissing the child on the mouth. 3. Respiratory viruses: such as influenza A (H1N1), human infection with highly pathogenic avian influenza, new coronavirus and other viruses. Therefore, it is generally not recommended to kiss the child’s mouth, and usually should pay attention to hygiene.