Primary dengue infection is characterised by the presence of significant or rising levels of IgM 3–5 days after the onset of infection, which can persist for 1–3 months, whereas secondary infection is characterised by elevated IgG levels, reaching a peak window of detection at 6–15 days after onset of symptoms and may also be accompanied by IgM [5], [9]. The gene discussed is CD40LG; the disease is infection.