Human microvirus B19 is a virus that causes infectious erythema or acute arthropathy. This virus can cause some blood diseases or immune impairment and other related problems, and its transmission is through the respiratory tract and blood. 1. Respiratory transmission: the main way of transmission of this virus is through the respiratory tract, but direct contact cannot be ruled out. 2. Blood transmission: If you have a wound and come into contact with people containing the virus, it is easy for the virus to enter the human body along with the wound, thus inducing infection. In addition, hemophilia, abnormal liver function, chronic intravascular coagulation and other related diseases. Patients need to use to coagulation factor concentrates for treatment, the same will also induce such viral infection. Human microvirus B19 is positive mainly through respiratory tract infection or contact infection, but does not rule out the blood cause.