A nonreactive IgM ELISA may not necessary mean absence of leptospirosis but it could be due to poor immune response as noted in neonates [26] or in the early phase of the disease when antibody levels have not been attained to a detectable amounts, which normally occurs 4–7 days after onset of the disease [5, 6]. The gene discussed is CD40LG; the disease is leptospirosis.