Characterising secondary dengue infections in Saudi Arabia using combined IgG and PCR testing.

BACKGROUND

Secondary dengue infection (SDI), often associated with increased disease severity, remains a diagnostic and public health challenge in endemic regions. This study evaluates the use of combined IgG and PCR testing in identifying SDI cases and explores the demographic, geographic and clinical characteristics of SDI in Saudi Arabia.

METHODS

A total of 2850 patient samples were collected from six regions in Saudi Arabia, from January 2022 to March 2024. Laboratory testing included NS1 antigen detection, IgM and IgG ELISA and RT-PCR for viral RNA. SDI was defined as IgG+/PCR+ based on the WHO criteria.

RESULTS

Of 1448 PCR-confirmed dengue cases, 493 (34%) were classified as SDIs. The highest proportions of SDIs were observed in Asir (71.4%), Jazan (60.0%) and Makkah (50.4%), with Makkah contributing the largest number of SDI cases overall (243/482). The highest burden was observed in males and individuals aged 21-40 y. Four deaths occurred among IgG+ patients with comorbidities.

CONCLUSIONS

Combined IgG and PCR profiling enhances the early identification of SDIs. Regional clustering and age-related patterns also underscore the need for targeted clinical monitoring and public health interventions.