Indian Ocean Temps Linked to Global Dengue Intensity

May 11, 2024

In recent research published in the journal Science, a noteworthy relationship has been identified between the sea-surface temperatures of the Indian Ocean and the global intensity of dengue outbreaks. This work introduces the Indian Ocean basin-wide (IOBW) index as a potential predictor for dengue epidemics, providing countries with vital lead time for preparation and response.

What is IOBW Index?

Indian Ocean Basin-Wide (IOBW) index is a climatological index used to monitor and predict climate variability in the Indian Ocean region. This index gauges the overall sea surface temperature anomalies (deviations from the norm) across the entire Indian Ocean basin. It is significantly valuable for understanding phenomena like the Indian Ocean Dipole and its impacts on regional climates and monsoon systems. The IOBW index helps in forecasting weather patterns, which is crucial for agricultural planning, water resource management, and disaster preparedness in surrounding countries, influencing their economies and ecosystems.

Researchers found that this index correlates closely with the occurrence of dengue outbreaks in both the Northern and Southern hemispheres. It was observed that higher index values (a positive index) enhance local temperature globally which in turn, potentially escalates dengue transmission.

Impact on Dengue Outbreaks

Dengue, primarily transmitted through Aedes mosquitoes, has expanded from 9 countries before 1970 to affecting nearly half of the global population today. The link between the IOBW index and dengue suggests that when the index is positive, there is a significant increase in dengue cases, and vice versa. This pattern holds true for both hemispheres, with a noted stronger correlation in the Southern Hemisphere.

Seasonal Variations and Geographic Disparities

Dengue epidemics peak between July and October in the Northern Hemisphere and from February to April in the Southern Hemisphere, corresponding with local summer periods. The study highlighted that countries like Brazil in the Southern Hemisphere are particularly affected, showcasing the index’s pronounced impact in tropical regions.

Challenges and Future Directions

While the initial findings are promising, the study acknowledges limitations such as the unavailability of comprehensive dengue incidence data from some countries and the exclusion of other influencing factors like vector control efforts and socio-economic conditions. Future research is recommended to include these variables to refine the early warning system for dengue more comprehensively. In conclusion, the IOBW index’s potential to forecast dengue outbreaks could revolutionize how health authorities globally anticipate and combat this disease, thereby mitigating its impact on public health.

GKToday Notes: Dengue

Dengue is a mosquito-borne viral infection prevalent in tropical and subtropical climates worldwide, mostly in urban and semi-urban areas. The disease is caused by the dengue virus (DENV), transmitted through the bites of infected Aedes mosquitoes, primarily Aedes aegypti. Symptoms include high fever, headache, vomiting, muscle and joint pains, and a characteristic skin rash. Severe forms can develop into dengue hemorrhagic fever, leading to bleeding, blood plasma leakage, and potentially fatal shock (dengue shock syndrome). Preventative measures focus on mosquito control and avoiding mosquito bites. Currently, there is one dengue vaccine, Dengvaxia, approved in several countries, but its use is limited to seropositive individuals due to concerns about effectiveness and safety in those who have never been infected.

GKToday Notes: Aedes species mosquitoes

Aedes mosquitoes are a genus primarily known for transmitting various major diseases including Zika, dengue fever, chikungunya, and yellow fever. These mosquitoes are easily identifiable by white markings on their legs and a marking in the form of a lyre on the upper surface of their thorax. Aedes species are particularly common in tropical and subtropical zones but have spread to other areas due to global trade and travel. Unlike other mosquitoes, Aedes typically bite during the day, particularly around dawn and dusk. Their capacity to breed in small amounts of water makes them difficult to control.

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