Dengue infections are imposing an increasing global burden of disease, particularly in tropical countries such as Bangladesh. The World Health Organization (WHO) has identified Dengue virus as a priority pathogen for the development of medical counter measures because of the high risk of it causing a Public Health Emergency of Intenational Concern (PHEIC). Warning signs for severe dengue, associated with mortality, include gastrointestinal features including abdominal pain, vomiting, and diarrhoea. Multiple alterations may occur in in the gastrointestinal tract that could lead to damaging of the gastrointestinal wall and gut leakage, the translocation of gut metabolites into the bloodstream. Study team hypothesize that gut leakage initiates inflammatory processes underlying the further development of severe dengue, including features associated with plasma leakage.

This study aims to investigate intestinal barrier dysfunction (gut leakage) in dengue infection by detecting the translocation of gut-derived bacteria and their products (Lipopolysaccharides, LPS binding protein, sCD14, I-Fatty Acid Binding Protein) into the bloodstream. Study team will recruit hospitalized adult dengue patients (18 years and older) presenting with warning signs or severe disease in a tertiary care public hospital at Chattogram, Bangladesh. Circulating biomarkers indicative of gut permeability and microbial translocation will be measured to assess their presence and association with disease severity.

Abdominal ultrasonography will be performed to characterize gastrointestinal alterations and determine their correlation with biochemical markers of gut leakage and clinical severity. In addition, study team will analyze the gut bacteriome from stool/ rectal swab of these patients to explore whether dengue infection induces compositional changes in intestinal microbiota and whether such alterations are linked to gut leakage or disease progression.

Inclusion Criteria:

Dengue participants

• Participant/ legally authorised representative willing and able to give informed consent for participation in the study.
• Male or Female, adults ≥18 years
• Diagnosed as a case of Dengue on the basis of clinical features and positive NS1 antigen and/or IgM dengue antibody
• Hospitalized in medicine or dengue ward in Chittagong Medical College Hospital.
• Enrolled within 24 hours of hospitalization.

Healthy participants

• Participant/ legally authorised representative willing and able to give informed consent for participation in the study.
• Male or Female, adults ≥18 years
• Clinically healthy with no acute or chronic illness
• Attendant of a dengue patient (not a patient)

Exclusion Criteria:

Dengue participants

• Unable to provide consent or participate in follow-up procedures
• Known chronic gastrointestinal (GI) disease affecting intestinal permeability (IBD, celiac disease), chronic liver disease, active chronic diarrhoea, short bowel loop syndrome, recent (<3 months) major GI surgery.
• Immunosuppression (for example chemotherapy, high-dose steroids), advanced chronic kidney disease, decompensated heart failure.
• Drugs that can alter the level of biomarkers in blood like metformin, statin, probiotics, steroid within last 48 hours of hospitalization.
• Pregnancy

Healthy participants

• Unable to provide consent
• Known chronic gastrointestinal (GI) disease affecting intestinal permeability (IBD, celiac disease), chronic liver disease, active chronic diarrhoea, short bowel loop syndrome, recent (<3 months) major GI surgery.
• Immunosuppression (for example chemotherapy, high-dose steroids), advanced chronic kidney disease, decompensated heart failure.
• Drugs that can alter the level of biomarkers in blood like metformin, statin, probiotics, steroid within last 48 hours of hospitalization.
• Pregnancy
• History of current or recent dengue or other arbo viral infection

Adult (≥18 years) male and non-pregnant female patients with confirmed dengue (positive NS1 antigen and/or IgM) admitted to the Department of Medicine, Chittagong Medical College Hospital will be recruited. Blood biomarkers will be collected at enrollment for all patients. Those initially classified as non-severe dengue will have no repeat sampling unless they progress to severe disease, in which case a second sample will be obtained within 24 hours. Serum ALT and blood culture will be performed on day 7 of illness. Stool samples will be collected on day 7 from 100 patients for gut microbiota analysis.

Additionally, 10 healthy adult participants (5 male, 5 female) will be recruited from patient attendants. They will undergo a single visit for baseline biomarker sampling and POCUS, serving as healthy controls for comparison.

Participant data and results from blood analyses stored in the database may be shared according to the terms defined in the MORU data sharing policy with other researchers to use in the future. Datasets will be de-identified to ensure patient privacy and confidentiality