One hundred and ten patients (M/F= 67/43) from King Chulalongkorn Memorial Hospital and the provincial hospitals of Uttaradit, Ayudhaya, and Sakonnakorn, who were clinically diagnosed with dengue infection and serologically confirmed by ELISA anti-Dengue IgM and IgG were recruited. Their serum NO level was measured using commercially available assay kits to investigate its correlation with the severity of the dengue infection: dengue fever (DF), DHF I/II, and DHF III/IV or dengue shock syndrome (DSS). Serum NO levels were also measured in 38 healthy controls (M/F= 19/19). Serum NO levels in dengue patients were lower than those of the controls (control= 168.18±24.10 µmol/l, DF= 124.94±36.79 µmol/l, DHF I/II= 99.69±33.42 µmol/l, and DHF III/IV= 120.63±46.26 µmol/l; p< 0.05). Serum NO levels in patients with DHF I/II were significantly lower than in those with DHF III/IV. These preliminary data revealed that levels of serum NO in dengue patients were significantly lower than those of normal controls. Patients with DSS had higher NO levels than those with DHF I/II. The decreased NO in dengue patients could be due to endothelial damage rendering the endothelium incapable of producing NO. Endothelial function seems to play a role in the pathogenesis of dengue infection. Further studies are required to see whether serum NO levels could play a role in the course of the disease and could help predict the severity of dengue infection.

The World Health Organization (WHO) estimates 50-100 million illnesses from dengue infection annually, including 250,000-500,000 cases of dengue hemorrhagic fever (DHF) and 24,000 deaths. In addition, more than two-fifths of the world’s population (2.5 billion people) live in dengue endemic or high-risk areas. 1 DHF has been a major cause of severe illness and death among children in Southeast Asia. The clinical picture is characterized by high continuous fever, hemorrhagic manifestations (positive tourniquet test, petechiae, epistaxis, hematemesis and melena), and hypovolemic shock in cases of dengue shock syndrome (DSS).