CD40LG and measles: For example, the detection of measles-specific IgM in the absence of recent vaccination is considered laboratory confirmation of measles in the United States, Japan, and England, whereas Canada requires epidemiologic linkage to a PCR positive measles case or known travel to an area of measles activity to consider IgM confirmatory, and Australian guidelines include IgM as “suggestive” but not confirmatory laboratory evidence of infection (Table 1).