FH and dengue disease: Compared to patients with dengue fever (DF), severely ill patients with dengue hemorrhagic fever (DHF) and dengue shock syndrome have been shown to have higher levels of C3 cleavage products, specifically fD, which cleaves fB to yield the active (C3bBb) C3 convertase, and lower levels of fH, which inactivates the C3 convertase31–33.