Rubella virus positive, in fact, most cases are diagnosed through blood tests for rubella virus IgG antibodies or IgM antibodies. It depends on which specific indicator is tested. If the IgM antibody is positive and the IgG antibody is negative, it indicates an ongoing infection. If both IgG and IgM antibodies are positive, it can be diagnosed as a rubella virus infection. If the IgG antibody is positive and the IgM antibody is negative, it indicates a past infection with no current rubella virus infection. If the rubella virus is cultured or detected in nasal secretions or blood, a definitive diagnosis can be made.