Cases were also categorized as dengue without warning signs (WS), dengue with WS, or severe dengue using WHO 2009 classifications [1] . Dengue (WHO 2009) requires fever and two of the following: nausea, vomiting, rash, aches and pains, leukopenia, or any warning sign [1] . Warning signs include abdominal pain or tenderness, persistent vomiting, clinical fluid accumulation, mucosal bleeding, lethargy or restlessness, hepatomegaly, or hematocrit rise ($20%) with rapid drop in platelet count (,50,000/liter) [1, 14] . We modified the WHO 2009 warning sign of rise in hematocrit concurrent with rapid drop in platelet count by quantifying it as hematocrit $20% concurrent with platelet count ,50,000/liter, as this was shown to correlate significantly with dengue death in our adult dengue death study [14] . Severe dengue includes severe plasma leakage, severe bleeding, and severe organ impairment [1] .