Molecular Characterization and Clinical Profile of Dengue Virus Serotypes in NS1-Positive Patients: A Cross-sectional Study from Rajkot, Gujarat, India

This cross-sectional study of 70 NS1-positive patients at AIIMS Rajkot from September 2023 to November 2024 reveals that DENV-2 is the predominant dengue serotype (75.7%) affecting young adults and children, with a notably low incidence of severe disease.

The Gist

🦟 The Big Picture: A Mosquito Mystery in Rajkot

Imagine the city of Rajkot, India, as a busy neighborhood. Recently, a sneaky invader called the Dengue Virus has been knocking on doors, carried by mosquitoes. This virus isn't just one thing; it's like a family with four different cousins (called Serotypes 1, 2, 3, and 4). Sometimes, they all show up at the same time, making it hard to know which one is causing the trouble.

This study is like a detective report from a local hospital (AIIMS Rajkot). The doctors wanted to answer three big questions:

1. Which "cousin" of the virus is currently the most popular?
2. Who is getting sick the most (kids, adults, men, women)?
3. How sick are people getting, and do we need to worry about a major outbreak?

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🔍 The Investigation: How They Caught the Culprit

The "NS1" Net:
First, the doctors used a quick screening test called NS1. Think of this like a metal detector at an airport. It's fast and catches most people with the virus, but it doesn't tell you exactly which cousin of the virus they have.

The "RT-PCR" Fingerprint:
To get the real identity, they took the blood samples from everyone who tested positive on the metal detector and sent them to a high-tech lab. There, they used a machine called RT-PCR.

• Analogy: If the NS1 test is a metal detector, the RT-PCR is like a DNA fingerprint scanner. It looks at the virus's genetic code and says, "Aha! This isn't just Dengue; this is specifically Dengue Type 2!"

The Result: Out of 70 patients they studied, 100% of the quick tests were confirmed by the fingerprint scanner. This means the quick test in their hospital is very reliable.

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🏆 The Winner: The "Big Bad" Cousin (DENV-2)

When they looked at the results, they found a clear winner.

• DENV-2 (The Boss): This was the most common virus, found in 76% of the patients. It was the "boss" of the outbreak.
• DENV-1 & DENV-3 (The Runners-up): These showed up in about 10% of cases each.
• DENV-4 (The Rare Guest): Only 2 people had this one.
• The Mix-Up: One unlucky patient had a "double trouble" infection (DENV-2 and DENV-3 at the same time).

Why does this matter?
Think of the virus cousins like different flavors of ice cream. If everyone has been eating "Flavor 1" for years, their bodies get used to it. But if "Flavor 2" suddenly takes over, people might get sicker because their bodies haven't seen it before. The study found that DENV-2 is currently the dominant flavor in Rajkot.

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👥 Who Got Sick? The "Who's Who" List

The study looked at the people in the hospital to see who was most affected:

• The "Young Adults" Club: The biggest group of sick people were young adults aged 19 to 35. Imagine a room full of college students and young workers; that's who was most affected.
• The Kids: Surprisingly, a large chunk (about 1/3rd) were children under 18. This is a red flag for parents and schools.
• Men vs. Women: There were slightly more men (about 60%) than women, but both were getting sick.

The Symptoms:
Almost everyone had a fever (100%). The most common complaints were:

• Headaches (feeling like a drum is beating inside your head).
• Rashes (skin looking like a sunburn).
• Feeling generally terrible (malaise).

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🚑 How Bad Was It? The "Severity" Gauge

Here is the good news: Most people were fine.

• 98.6% of the patients had "uncomplicated" dengue. They felt awful for a few days, but they recovered without major issues.
• Only one person (1.4%) got "Severe Dengue." This is the dangerous kind where the body starts leaking fluid or bleeding.
• About 36% of people needed to stay in the hospital, mostly because their platelet counts (the blood cells that stop bleeding) dropped too low.

The "Platelet" Analogy:
Think of platelets as the construction workers in your blood who patch up leaks. When you have dengue, the virus kicks the workers out of the job site. If the number of workers drops too low (below 150,000), the "leaks" (bleeding) can start. The study found that the lower the platelet count, the more likely a person was to need hospital care.

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🌧️ The Weather Connection

The study noticed that the number of sick people spiked right after the monsoon rains (September to November).

• Analogy: Mosquitoes are like weeds. When it rains, the "weed beds" (puddles and stagnant water) fill up, and the mosquitoes (the weeds) grow like crazy. The study confirmed that when the rain stops, the virus party starts.

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💡 What Does This Mean for Us? (The Takeaway)

1. The "Boss" is DENV-2: In Rajkot right now, if you get dengue, it's most likely the Type 2 cousin.
2. Don't Ignore the Kids: A huge number of children are getting sick. Schools and homes need to be extra careful about stopping mosquitoes.
3. Early Detection Works: The hospital's quick test (NS1) works perfectly to catch the virus early, which helps doctors treat patients before they get too sick.
4. Stay Vigilant: Even though only one person got "severe" dengue in this study, the fact that the "dangerous" cousin (DENV-2) is so common means we can't let our guard down. If the virus changes or people get infected a second time, things could get worse.

In short: The virus is here, it's mostly Type 2, it's hitting young adults and kids hard, but thanks to good testing and care, most people are recovering well. The best defense? Keep the mosquitoes away! 🦟🚫

Technical Summary

Title

Molecular Characterization and Clinical Profile of Dengue Virus Serotypes in NS1-Positive Patients: A Cross-sectional Study from Rajkot, Gujarat, India

1. Problem Statement

Dengue virus (DENV) infection is a major public health challenge in India, characterized by changing serotype dynamics that influence disease epidemiology and severity. While the NS1 antigen rapid test is widely used for early diagnosis, it does not identify the specific serotype (DENV-1 to DENV-4). Understanding the local distribution of serotypes is critical for predicting outbreak patterns, assessing the risk of severe disease (often associated with secondary infections and Antibody-Dependent Enhancement), and planning public health responses. There was a lack of comprehensive molecular characterization data regarding dengue serotypes specifically from the Saurashtra region of Gujarat, particularly from tertiary care centers.

2. Methodology

• Study Design: A cross-sectional observational study conducted following STROBE guidelines.
• Setting & Population: Conducted at AIIMS Rajkot, a tertiary care hospital serving the Saurashtra region. The study included 70 NS1 antigen-positive patients admitted between September 2023 and November 2024.
• Inclusion/Exclusion: All ages with confirmed NS1 positivity were included; patients with incomplete data or lack of consent were excluded.
• Sample Collection: Venous blood (3–5 ml) was collected within 1–7 days of fever onset. Serum was stored at -80°C.
• Diagnostic Workflow:
  1. Screening: NS1 antigen detection via rapid diagnostic tests and Monalisa ELISA.
  2. Molecular Confirmation: Viral RNA extraction followed by Real-time RT-PCR using the RealStar® Dengue Type RT-PCR Kit 1.0 (Altona Diagnostics).
  3. Serotyping: Specific primers and probes for DENV-1, DENV-2, DENV-3, and DENV-4 were used. A Cycle threshold (Ct) value ≤40 was considered positive.
• Data Analysis: Demographic, clinical, and laboratory data were collected. Statistical analysis (SPSS v26) included descriptive statistics, Chi-square tests, and multivariable logistic regression to identify factors associated with hospitalization.

3. Key Contributions

• Regional Epidemiology: Provides the first comprehensive molecular serotype data from a tertiary care center in the Saurashtra region of Gujarat.
• Validation of Screening: Confirms the high concordance (100%) between NS1 antigen screening and RT-PCR confirmation in the early phase of illness (days 1–7).
• Clinical Correlation: Links specific serotypes (predominantly DENV-2) with clinical outcomes and demographic profiles in a specific Indian sub-region.
• Surveillance Baseline: Establishes a baseline for hyperendemic transmission patterns (presence of all four serotypes) in the region.

4. Key Results

• Serotype Distribution:
  • DENV-2 was the overwhelmingly predominant serotype, accounting for 53 cases (75.7%).
  • DENV-1 and DENV-3 each accounted for 7 cases (10.0%).
  • DENV-4 was found in 2 cases (2.9%).
  • Co-infection: One case (1.4%) involved simultaneous infection with DENV-2 and DENV-3.
  • The presence of all four serotypes confirms hyperendemic transmission in the region.
• Demographics:
  • Age: Mean age was 27.7 ± 14.4 years. The most affected group was young adults (19–35 years, 45.7%), followed by pediatrics (≤18 years, 32.9%).
  • Gender: Male predominance was observed (58.6%).
• Clinical Outcomes:
  • Severity: Only 1 case (1.4%) developed severe dengue (associated with DENV-2). No cases of Dengue Shock Syndrome (DSS) or Dengue Hemorrhagic Fever (DHF) were observed.
  • Hospitalization: 35.7% of patients required hospitalization. Multivariable analysis identified decreased platelet counts as the only independent predictor of hospitalization (OR 0.84 per 10,000/µL increase; p=0.0009). Age and Ct values were not significant predictors.
  • Symptoms: Fever was universal. Other common symptoms included headache (50%), rash (56%), and malaise (56%).
  • Laboratory: Thrombocytopenia (<150,000/µL) was present in 67.1% of patients.
• Temporal Pattern: Cases peaked during the post-monsoon months (September–November), correlating with rainfall patterns.

5. Significance and Implications

• Public Health Strategy: The dominance of DENV-2 suggests a high risk for severe secondary infections if other serotypes become prevalent later, due to Antibody-Dependent Enhancement (ADE). This necessitates vigilant surveillance.
• Targeted Interventions: The significant involvement of young adults and children highlights the need for vector control measures specifically targeting residential areas and schools.
• Clinical Management: The low rate of severe disease despite DENV-2 dominance suggests that early diagnosis (via NS1) and appropriate clinical management at the tertiary level are effective. However, the study emphasizes that hospitalization decisions should remain based on clinical warning signs and platelet counts rather than serotype alone.
• Future Directions: The authors recommend multi-center surveillance, serological studies to distinguish primary vs. secondary infections, and genetic characterization of circulating strains to better understand viral evolution and virulence.

Conclusion: The study confirms DENV-2 as the dominant circulating serotype in Rajkot, Gujarat, during the 2023–2024 period. While the overall severity was low, the hyperendemic nature of the region and the specific demographic vulnerabilities underscore the necessity for continued molecular surveillance and targeted prevention strategies.