Wolbachia releases bring hope to Cali in worst year on record for dengue fever worldwide

In the sizzling salsa capital of the world, there is a hypnotic rhythm and vibrant authenticity which makes Santiago de Cali, known simply as Cali, such a unique and absorbing tropical metropolis.

Colombia’s third-most populous city is located between the Western and Central mountain ranges of the Andes — in the valley of the Cauca River — roughly 1,000 metres above sea level. Founded by the Spanish in the 1530s, Cali’s thriving mix of gastronomy, culture and music draws on European, African and Indigenous roots.

Cali’s Urban Growth and Dengue Fever Outbreaks

In recent years, the city has not only seen a significant growth in tourism, but also a population boom. Increased urbanisation and migration from neighbouring regions hasn’t come without its challenges, as local services such as healthcare, education and employment opportunities have become stretched.

The city has also been faced with an unprecedented year of dengue outbreaks, reflected across the Valle del Cauca State, where Cali resides. In May, state health authorities had already reported more than 52,000 dengue cases, compared with 23,000 for all of 2023 and 5,000 in 2022.

World Mosquito Program Launches Final Phase of Wolbachia Releases in Cali

The World Mosquito Program (WMP) has been working in partnership with the District Health Secretariat since 2019, protecting more than 1.1 million people in Cali. In June, WMP embarked on its fourth and final phase of Wolbachia mosquito releases in the north of the city, working with the ESE Norte, Ladera and Centro, to protect eight communes and cover around 42km².

The releases, which are due to finish in the next few weeks, will see more than 75 per cent of the city protected from mosquito-borne diseases.

It arrives at a time when Latin America is reeling from its worst year on record for dengue cases.

So far, the European Centre for Disease Prevention and Control (ECDC) reports more than 14 million dengue cases worldwide and over 10,000 dengue-related deaths, with the Centre for Disease Control and Prevention (CDC) recording 12 million cases in the Americas alone.

Colombia has more than 290,000 cases — the fifth highest in the world in 2024.

Success in Aburrá Valley Offers Hope for Cali

However, one region that has defied odds in Colombia over the past year has been the Aburrá Valley, where dengue fever cases have dropped to a 20-year low. This follows WMP’s city-wide deployments of Wolbachia mosquitoes between 2015 and 2022 in Bello, Medellín and Itagüi. Dengue incidence rates have dropped by at least 95 per cent. It is a feat which Cali health authorities hope can be replicated in the city.

“We are facing the worst dengue epidemic in the Americas this year, aggravated by climate change,” says Alejandro Eder, Mayor of Cali.

He continues: “In Cali, we are using innovative methods, working with the World Mosquito Program’s natural solution that has already demonstrated its success in Medellín. This international alliance marks a milestone in our tireless fight against dengue.

“With the implementation of the fourth phase, we will reach a more protected city, and we hope that this will be the last major peak of dengue we will face.”

The final phase of the Cali Wolbachia releases will see more than 750,000 people in the north of the city protected in comunes 2 - 9. Official data from the previous phases show a decrease in dengue cases somewhere between 41 and 54 per cent in treated areas.

“This project not only complements our existing efforts, but represents a qualitative leap in our prevention capacity," says District Secretary of Public Health, Germán Escobar. “This success is not only reflected in the statistics, but in the daily life and health of the people of Cali.”

Optimism for a Dengue-Free Future

Jaime Andrés Ramírez, the Cali project coordinator for WMP, says the More Wolbachia, Less Dengue! campaign has been a thoroughly collaborative effort with community leaders, institutional allies and a “solid foundation of community participation.”

He says the project in Cali has, however, faced a series of complex challenges, from the global pandemic to the social and political dynamics of the city.

“We have learned that the key to success, in addition to hard work, is the ability to adapt to the circumstances, to build relationships based on trust, as well as linking the community, the various allied institutions and team members, in all stages of the process," says Ramírez.

Ramírez believes the releases in Cali can serve as a model for other similar projects, demonstrating that it is possible to implement successful interventions in complex and challenging contexts. As releases conclude in the coming weeks, optimism is high in the city, as many hope for a brighter future free from mosquito-borne diseases.

“The scientific evidence of the effectiveness of this programme is overwhelming,” says Carlos Pinzón, the under-secretary of District Health in Cali. “We hope to have fewer positive dengue cases in the future.”