NS 1 lasts longer than the dengue virus nucleic acid in the clinically suspected patients with dengue fever and dengue haemorrhagic fever.

The objectives of the study were to compare the DENV NS1 and nucleic acid positivity in dengue fever (DF) and dengue haemorrhagic fever (DHF) patients and to evaluate the usefulness of these parameters in severe dengue. Blood samples were collected from 91 patients with DF or DHF (fever days 3-9) from Gampaha and Negombo General Hospitals, Sri Lanka and tested for DENV NS1 antigen and nucleic acid. On fever day 3, 67% of the DF and 33% of the DHF patients had DENV nucleic acid whereas 50% of the DF and 67% of the DHF patients had NS1. On fever day 4, 67% of the DF and 100% of the DHF patients had DENV nucleic acid whereas 83% of the DF and DHF patients had NS1. From fever day 5 in the DHF group, DENV nucleic acid declined but NS1 remained detectable even on day 9 (p < 0.0001). NS1 positivity did not correlate with the decrease in the WBC count in DF and DHF patients (p > 0.05) whereas NS1 positivity significantly correlated with the decrease in the platelet count in DF and DHF patients (p < 0.0001). NS1 is a useful marker to detect DENV infection even in the latter stages of DHF.