El Nino effect: Cases of dengue have increased globally

Subject : Geography

Section: Climatology

In the news:

The World Health Organization (WHO) reported a staggering ten-fold increase in dengue cases globally between 2000 and 2019, rising from 500,000 to 5.2 million reported cases. However, this count likely underestimates the actual prevalence due to many cases being asymptomatic and the disease not being notifiable in numerous countries.

Details:

Following a decline during the pandemic years (2020-2022), there was a sharp resurgence in global dengue cases in 2023. Over 5 million cases and more than 5,000 deaths were reported across 80 countries. The North and SouthAmerica bore the brunt, with 4.1 million suspected cases, notably impacting Brazil, Peru, and Mexico.
In 2023, the upsurge can be linked to the changing distribution of the vectors (chiefly Aedes aegypti and Aedes albopictus); increase in temperature and changes in rainfall patterns due to the El Nino climate phenomenon; fragile health systems after the pandemic, political and financial instabilities in countries; and high population movements.

Global spread:

Southeast Asia witnessed a notable surge, particularly in Bangladesh and Thailand. In Africa, 171,991 cases were reported, with Burkina Faso facing the most severe impact.
The Eastern Mediterranean saw dengue spreading to nine countries, notably affecting Pakistan, Saudi Arabia, and Oman. In the European Region, dengue, once mainly travel-related, has established itself since 2010, with cases reported in Italy, France, and Spain.
The Western Pacific Region reported over 500,000 cases and 750 deaths, primarily affecting the Philippines, Vietnam, and Fiji.
To address outbreaks, a Global Joint Incident Management Support Team was established, combining WHO Health Emergencies Programme departments and expertise from the neglected tropical disease department.
Dengue transmission involves four serotypes of the virus (DENV-1, DENV-2, DENV-3, DENV-4), contributing to cyclic outbreaks occurring every 3-4 years.

About Dengue:

It is caused by the dengue virus (DENV).
It is transmitted to humans through the bites of infected female mosquitoes, primarily the Aedes aegypti mosquito.
The severe form of dengue fever, also called dengue hemorrhagic fever, can cause serious bleeding, a sudden drop in blood pressure (shock) and death.
It is more common in tropical and subtropical climates.
Symptoms: The most common symptoms are high fever, headache, body aches, nausea and rash.
Most will also get better in 1–2 weeks but in severe cases it can be fatal.
Treatment:
- There is no specific treatment for dengue.
- Early detection of disease progression associated with severe dengue, and access to proper medical care lowers fatality rates of severe dengue to below 1%.
- The dengue vaccine CYD-TDV or Dengvaxia was approved by the US Food & Drug Administration in 2019, the first dengue vaccine to get the regulatory nod in the US.