Concurrent Dengue Strains Fuel Severe Outbreaks as Multiple Serotypes Sweep India

Rising Complexity in India’s Dengue Profile

Data from a two-year nationwide surveillance initiative indicate that India has transitioned into a hyper-endemic phase of dengue transmission. The study, conducted by the Indian Council of Medical Research (ICMR) Virus Research and Diagnostic Laboratory (VRDL) network, reveals that all four dengue serotypes (DENV-1 through DENV-4) are currently circulating in several regions simultaneously. This concurrent presence of multiple strains complicates the clinical outlook for millions of residents.

The research, titled 'Pan-India Molecular Surveillance of Dengue Serotypes, 2023–2025,' scrutinized 6,889 confirmed samples across 25 States and Union Territories. While DENV-2 remains the primary driver of infections, accounting for over 50% of the cases analyzed, the coexistence of other strains represents a shifting epidemiological pattern.

Clinical Risks of Concurrent Infections

One of the most concerning revelations is that roughly 7% of patients—approximately one in 14—are infected with two or more serotypes at the same time. The data suggests these concurrent infections correlate with more aggressive disease progression. Key clinical findings regarding these multi-strain infections include:

• Higher frequency of dangerously low platelet counts.
• Increased instances of internal bleeding and complications.
• Greater prevalence of debilitating joint pain compared to single-strain infections.

While DENV-2 is historically associated with severe outbreaks, researchers emphasize that the risk of severe disease often spikes during a secondary infection with a different serotype. The current spread means eight States and Union Territories now host all four serotypes, while another 15 regions reported three strains active at once.

Implications for Vaccine Strategies

The shifting viral landscape presents a significant hurdle for public health officials preparing for large-scale immunization. Although India has not yet integrated a dengue vaccine into its Universal Immunisation Programme, several domestic candidates are currently in advanced clinical trials. Additionally, a foreign-developed vaccine recently secured regulatory approval for the Indian market.

Gautam Menon, Professor of Physics and Biology at Ashoka University, argues that vaccination efforts must be supported by permanent, real-time surveillance. Because vaccine efficacy fluctuates depending on the specific strain, experts warn that any sudden shift in the dominant serotype could undermine a localized immunization campaign. Menon suggests that identifying hotspots and monitoring serotype shifts should become a standardized, ongoing public health function to provide early warnings for potential outbreaks.

Source: The Hindu — National