A cough (initially nonproductive) typically signals the transition to the cardiopulmonary phase, in which a fulminant capillary leak syndrome leads to rapidly progressive pulmonary edema and shock. As seen in our patient, this transition can occur rapidly, in as little as 4 h, and has led to recommendations for the transfer of these patients to tertiary care centers at the earliest signs of HPS. Bronchorrhea with copious proteinaceous edema fluid, with or without diffuse alveolar hemorrhage, can be seen. Laboratory findings during this phase include marked leukocytosis with a leftward shift, worsening thrombocytopenia, elevated serum lactate dehydrogenase and aspartate aminotransferase, hemoconcentration, and low serum albumin due to capillary leak. Additional findings on the peripheral blood smear that are highly suggestive of HPS include a relative lack of toxic granulation of the neutrophils, and immunoblasts accounting for ≥10% of the total lymphocyte population. An elevated serum lactate level, which is associated with poor outcome, can be seen in severe cases; in one early series, all patients with a peak serum lactate concentration of >4 mmol/L died.