A wide spectrum of dengue IgM and PCR positivity post-onset of illness found in a large dengue 3 outbreak in Pakistan.

During a large outbreak of dengue serotype 3 in Pakistan in 2006, multiple serum samples were routinely collected for laboratory testing. Two hundred ninety-seven samples were collected between August and November 2006. Serological testing for dengue IgM was performed in Pakistan and polymerase chain reaction (PCR) testing for dengue RNA detection and serotyping were performed in Hong Kong. Dengue-specific IgM was detectable as early as 1 day, and dengue RNA remained detectable for up to 14 days, post-onset of illness. Further statistical analysis found that IgM status (positive, negative, or equivocal) was significantly correlated to clinical (duration of illness, severity of patient-reported arthralgia pain, the presence of any evidence of bleeding, a positive tourniquet test, shock), and other laboratory (platelet and total white cell counts) parameters. In contrast, the qualitative dengue RNA status (PCR positive or negative) was not statistically significantly correlated with any of these other parameters. The results for this population during this outbreak, obtained from single acute samples, demonstrate a wide range of intervals post-onset of illness during which dengue IgM and dengue RNA may be detected. Interestingly, in this study, the dengue IgM positivity correlates more closely with significant clinical illness than the dengue RNA positivity, which may be a feature specific to this particular outbreak.