Positive IgM and IgG tests for dengue antibodies detected in an initial blood sample mean that it is likely that the person became infected with dengue virus within recent weeks. IgM antibody tests can be positive if a person has been infected with a similar virus, such as chikungunya (called cross-reaction)The IgM become detectable on Day 3 to 5 of illness in case of primary dengue infection and persist for 2 to 3 months, whereas IgG appear by the fourteenth day and persist for life. Secondary infection shows that IgG rises within 1 to 2 days after onset of symptoms, simultaneously with IgM antibodies.