Author: Yanni Yoong (Sr Program Mgr), Evdoxia Kakani, PhD (Staff Scientist), Monica Tsai (BD)


Following positive results from release of male Wolbachia-carrying Aedes aegypti in Singapore, we are happy to announce that Debug is supporting the expansion of Project Wolbachia in Singapore to cover 5 new residential sites to increase Project Wolbachia’s coverage from 350,000 households in 2023 to 480,000 households by Q1 2024 - an increase from 26% to 35% of households in Singapore.



Results from NEA’s Project Wolbachia – Singapore

Aedes aegypti mosquito populations in the existing study sites of Bukit Batok, Choa Chu Kang, Tampines (releases done by Debug by Verily since 2018), and Yishun have generally fallen by more than 90 per cent. Data from 2019 to 2022 indicates that residents living in areas with at least one year of releases were up to 77 per cent less likely to be infected with dengue.


Results from Debug’s release areas. 

The heatmaps in Tampines and Marine Parade below show the “eraser effect” where releases of male Wolbachia-Aedes mosquitoes has decreased the dengue risk over time.



Source: NEA website


The increased capacity for Project Wolbachia from 7 million in 2023 to 11 million male Wolbachia-Aedes mosquitoes produced and released weekly is made possible by Singapore’s National Environment Agency (NEA) and its collaboration with Debug.  By the end of Q1 2024, Debug will be producing and releasing more than 6 million male Wolbachia-Aedes mosquitoes per week for Project Wolbachia in Singapore .


Debug has been using its proprietary automation technology for the production, sex-sorting, and release of male Wolbachia-Aedes mosquitoes at the Tampines and Marine Parade study sites since 2023, following a collaborative research from 2018 to 2023.  


Verily's Program Manager Yanni Yoong explaining to Senior Minister of State for National Development and Foreign Affairs Sim Ann and pre-school children how male male Wolbachia-Aedes mosquitoes are released via hand containers at the expansion of Project Wolbachia in Clementi residential estate.
Verily's Program Manager Yanni Yoong explaining to Senior Minister of State for National Development and Foreign Affairs Sim Ann and pre-school children how male male Wolbachia-Aedes mosquitoes are released via hand containers at the expansion of Project Wolbachia in Clementi residential estate.


Male Wolbachia-Aedes mosquitoes are released using Debug’s vans to efficiently cover larger areas and evenly disperse mosquitoes among the blocks.
Male Wolbachia-Aedes mosquitoes are released using Debug’s vans to efficiently cover larger areas and evenly disperse mosquitoes among the blocks.

1Around 4 million male Wolbachia-Aedes mosquitoes for the expansion sites and around 2 million for the existing sites (Tampines and Marine Parade) are produced and released weekly.

Author: Yanni Yoong (Sr Program Mgr), Evdoxia Kakani, PhD (Staff Scientist), Monica Tsai (BD)


Following positive results from release of male Wolbachia-carrying Aedes aegypti in Singapore, we are happy to announce that Debug is supporting the expansion of Project Wolbachia in Singapore to cover 5 new residential sites to increase Project Wolbachia’s coverage from 350,000 households in 2023 to 480,000 households by Q1 2024 - an increase from 26% to 35% of households in Singapore.



Results from NEA’s Project Wolbachia – Singapore

Aedes aegypti mosquito populations in the existing study sites of Bukit Batok, Choa Chu Kang, Tampines (releases done by Debug by Verily since 2018), and Yishun have generally fallen by more than 90 per cent. Data from 2019 to 2022 indicates that residents living in areas with at least one year of releases were up to 77 per cent less likely to be infected with dengue.


Results from Debug’s release areas. 

The heatmaps in Tampines and Marine Parade below show the “eraser effect” where releases of male Wolbachia-Aedes mosquitoes has decreased the dengue risk over time.



Source: NEA website


The increased capacity for Project Wolbachia from 7 million in 2023 to 11 million male Wolbachia-Aedes mosquitoes produced and released weekly is made possible by Singapore’s National Environment Agency (NEA) and its collaboration with Debug.  By the end of Q1 2024, Debug will be producing and releasing more than 6 million male Wolbachia-Aedes mosquitoes per week for Project Wolbachia in Singapore .


Debug has been using its proprietary automation technology for the production, sex-sorting, and release of male Wolbachia-Aedes mosquitoes at the Tampines and Marine Parade study sites since 2023, following a collaborative research from 2018 to 2023.  


Verily's Program Manager Yanni Yoong explaining to Senior Minister of State for National Development and Foreign Affairs Sim Ann and pre-school children how male male Wolbachia-Aedes mosquitoes are released via hand containers at the expansion of Project Wolbachia in Clementi residential estate.
Verily's Program Manager Yanni Yoong explaining to Senior Minister of State for National Development and Foreign Affairs Sim Ann and pre-school children how male male Wolbachia-Aedes mosquitoes are released via hand containers at the expansion of Project Wolbachia in Clementi residential estate.


Male Wolbachia-Aedes mosquitoes are released using Debug’s vans to efficiently cover larger areas and evenly disperse mosquitoes among the blocks.
Male Wolbachia-Aedes mosquitoes are released using Debug’s vans to efficiently cover larger areas and evenly disperse mosquitoes among the blocks.

1Around 4 million male Wolbachia-Aedes mosquitoes for the expansion sites and around 2 million for the existing sites (Tampines and Marine Parade) are produced and released weekly.

Author: Jo Ohm, Scientist 

We are excited to announce that the Verily Debug team is starting a collaboration with the BugOut program on Virgin Gorda in the British Virgin Islands. BugOut is a community-driven vector control initiative with the mission to reduce Aedes aegypti mosquitoes in the Territory. Aedes aegypti is invasive in the BVI and is both a vector of dengue, Zika and chikunguyna diseases, and a significant nuisance pest. The BugOut program is managed by Green VI, a BVI-based non-profit that works on environmental programs including waste management and environmental education.

Author: Jo Ohm, Scientist 

We are excited to announce that the Verily Debug team is starting a collaboration with the BugOut program on Virgin Gorda in the British Virgin Islands. BugOut is a community-driven vector control initiative with the mission to reduce Aedes aegypti mosquitoes in the Territory. Aedes aegypti is invasive in the BVI and is both a vector of dengue, Zika and chikunguyna diseases, and a significant nuisance pest. The BugOut program is managed by Green VI, a BVI-based non-profit that works on environmental programs including waste management and environmental education.

BugOut’s aim to reduce Aedes aegypti mosquitoes ties in with Green VI’s other environment-focused initiatives, and piggybacks off the waste management effort to clean up neglected containers and piled trash that become breeding grounds for mosquitoes. Through targeted education, data-driven field work, and a consistent community presence, Green VI’s BugOut has successfully reduced mosquito breeding sites by 50% over the past 5 years. Debug is partnering with BugOut to launch the next phase of their program to further reduce Aedes aegypti mosquitoes using a Wolbachia-based incompatible insect technique (IIT). We are excited to be on board and looking forward to working on a unique and synergistic approach to mosquito control.

The Debug-BugOut partnership is launching as BugOut Wolbachia and combines Debug’s expertise in Wolbachia-male releases with BugOut’s ongoing efforts to rid the community of larval breeding sites. We will use our combined sets of tools to suppress Aedes aegypti on BVI in a way that follows Green VI’s environmentally-conscious and community-driven mission.


We will spend the next several months supporting Green VI’s BugOut team and their community representatives as they evaluate how to integrate a Wolbachia-male Aedes aegypti release program into their toolkit. Our BugOut Wolbachia collaboration started collecting data on the existing mosquito population on Virgin Gorda in February 2022. We have begun engaging with the community to share knowledge of how Wolbachia works and how it can be used to reduce mosquitoes and hopefully mosquito-borne disease in the BVI. We have also been working with the community on preliminary studies of released Wolbachia male mosquitoes to evaluate their ability to survive and disperse in the field. Virgin Gorda will be the first island in the BVI to pilot the BugOut Wolbachia program as we learn and adapt our methods to match the unique needs of the local community and mosquito population before potentially scaling to other parts of the Territory.

We look forward to the start of a shared venture in reducing Aedes aegypti on Virgin Gorda with BugOut Wolbachia. Fewer mosquitoes in the BVI will help reduce the incidence of mosquito-borne diseases but also promises to reduce nuisance biting, enhance tourism, and diversify the BugOut toolkit with an additional non-toxic, eco-friendly approach to mosquito control.







On September 15, the Debug team welcomed Singapore Prime Minister Lee Hsien Loong to our operations in Singapore, as part of his tour of the National Environment Agency (NEA) - Environmental Health Institute (EHI) Mosquito Production Facility. In addition to ongoing threats from Covid-19, dengue remains a top priority in Singapore, and his tour highlighted the importance of developing novel tools such as Project Wolbachia – Singapore to prevent the spread of dengue.

On September 15, the Debug team welcomed Singapore Prime Minister Lee Hsien Loong to our operations in Singapore, as part of his tour of the National Environment Agency (NEA) - Environmental Health Institute (EHI) Mosquito Production Facility. In addition to ongoing threats from Covid-19, dengue remains a top priority in Singapore, and his tour highlighted the importance of developing novel tools such as Project Wolbachia – Singapore to prevent the spread of dengue.

Prime Minister Lee saw first hand some of the tools that have enabled the success of Project Wolbachia – Singapore, in which Verily has partnered with the NEA-EHI since 2018. As part of the program, Verily has released male Wolbachia-carrying Aedes aegypti mosquitoes in parts of Tampines town and has achieved a greater than 90% reduction in mosquito population, resulting in 65-80% reduction in dengue cases.

We were honored to demonstrate our technology to Prime Minister Lee and Mrs. Lee, who joined him on the tour. Together they visited our Sex Sorting Room, currently housed within the NEA-EHI Mosquito Production Facility and took a deep dive into understanding our mosquito sex-sorting technology, which has been successfully used in Debug Fresno and Debug Innisfail to separate male and female mosquitoes using a computer vision algorithm and artificial intelligence.

Prime Minister Lee Hsien Loong and Mrs. Lee taking a closer look at Verily sex sorters

We are excited to continue to deploy our engineering and scientific capabilities to support NEA-EHI in scaling up production, sex sorting and release of male Wolbachia-carrying Aedes aegypti mosquitoes over the years to come.

Debug team members with Prime Minister Lee Hsien Loong (center) and Mrs. Lee ( right of center)



Yanni Yoong, Program Manager, Debug; Hyegi Chung, Country Lead, Verily

Today, we are excited to announce that Debug will be participating in Communities Organized for the Prevention of Arbovirus (COPA) based in Ponce, Puerto Rico. COPA is a community-based project to prevent diseases transmitted by mosquitoes. A central component of the project is a large epidemiological randomized control trial (RCT) to evaluate methods for suppressing mosquito populations and whether they can reduce the incidence of human arboviral infection. Debug was selected by the COPA steering committee to implement a ...
Today, we are excited to announce that Debug will be participating in Communities Organized for the Prevention of Arbovirus (COPA) based in Ponce, Puerto Rico. COPA is a community-based project to prevent diseases transmitted by mosquitoes. A central component of the project is a large epidemiological randomized control trial (RCT) to evaluate methods for suppressing mosquito populations and whether they can reduce the incidence of human arboviral infection. Debug was selected by the COPA steering committee to implement a Wolbachia-based sterile insect technique (SIT) for this trial to evaluate the extent to which SIT can reduce Aedes aegypti in Ponce release neighborhoods and reduce diseases like dengue and Zika, when coupled with community education.



This project is in collaboration with the Puerto Rico Vector Control Unit (PRVCU), who will be running the release program in Ponce using Debug technology and WB1 Wolbachia mosquitoes (through our partnership with MosquitoMate), Ponce Health Sciences University, and the Centers for Disease Control and Prevention (CDC), who will be independently collecting epidemiological data from residents in both the release and control neighborhoods.

Credit: Jose Oquendo - Own work, CC BY-SA 3.0




Our ability to contribute to this important evaluation is based on several successful Debug field trials, which demonstrated a considerable reduction in the Ae. aegypti mosquito populations in areas of California, Singapore and Australia. Like our other field releases, Debug technology will be used to rear and release male Ae. aegypti mosquitoes with Wolbachia - a naturally occurring bacterium. When our male mosquitoes mate with local female Ae. aegypti mosquitoes, their eggs do not hatch, reducing the population over time. Our participation in COPA represents Debug’s first opportunity to directly assess, through an RCT, the impact of our approach on human disease outcomes, with the hope of reducing the incidence of diseases spread by Ae. aegypti. Puerto Rico has endured a number of large arboviral outbreaks in recent years, including major dengue epidemics in 2010, 2012-2013, chikungunya in 2014, and a large Zika outbreak in 2016.

Yearly Arboviral Confirmed and Probable Cases, Puerto Rico, 2007- 2020. Data sources: dengue: PAHO, confirmed and probable cases, chikungunya: PRDH, confirmed and probable cases, Zika: PAHO, confirmed and probable cases, last updated: July 17, 2020.





For COPA, we are very fortunate to build on multiple years of work from PRVCU and the CDC whose efforts with community outreach, mosquito surveillance, trial design, and serological testing form the strong foundation upon which this evaluation can take place. Our partnership has commenced releases for the COPA RCT, which consists of 12 neighborhood zones where mosquito and serological surveillance has been performed. Clusters within these 12 zones have been randomly selected to receive Debug’s Wolbachia-based SIT and the remaining areas will act as controls.

12 neighborhood zones in the COPA RCT in Ponce, Puerto Rico




This is an important next step for Debug, as we deploy our technique for the first time in this region where diseases spread by Ae. aegypti pose a consistent threat to human health and wellness. We are thrilled to partner with local and national experts in this program as we work together to hopefully see a significant, positive impact on the health of people in Ponce.



Sara N Mitchell, PhD, Senior Scientist, Verily

Today, our scientific paper reporting near-elimination of Aedes aegypti from three neighborhoods in Fresno County, California was published in the journal Nature Biotechnology. While we previously summarized the impressive topline results of our Debug Fresno program, the peer-reviewed paper provides extensive new details regarding our field study design, mosquito rearing and release technology, trapping data, and analysis methods. The general public, mosquito control community, governmental stakeholders, and regulators alike can now independently review our methods and results.
Today, our scientific paper reporting near-elimination of Aedes aegypti from three neighborhoods in Fresno County, California was published in the journal Nature Biotechnology. While we previously summarized the impressive topline results of our Debug Fresno program, the peer-reviewed paper provides extensive new details regarding our field study design, mosquito rearing and release technology, trapping data, and analysis methods. The general public, mosquito control community, governmental stakeholders, and regulators alike can now independently review our methods and results.



Debug-built sex sorters achieve unprecedented accuracy by classifying individual males and females using industrial vision and machine learning algorithms.



Of particular interest, the manuscript reveals formerly undisclosed features and performance metrics of our automated mosquito production and release tools. In the paper, we describe how we reared mosquito larvae in disposable, thermoformed plastic containers, resulting in unprecedented consistency in male mosquito production. We also provide a step-by-step breakdown of our automated sex separation process including calculations of accuracy at each step. For the end-to-end process, we achieved a remarkable level of accuracy that is orders of magnitude better than manual sex separation methods. On the release side, we provide visualizations of how custom software guides male mosquito releases from our vans and allows us to detect and target those areas where releasing additional male mosquitoes would further improve program effectiveness. In addition to these metrics and descriptions, we are releasing all of the field data we collected during the course of the study to allow for analytical replication.

Debug Fresno was an incredibly rewarding partnership among ourselves, the Consolidated Mosquito Abatement District, MosquitoMate, and the residents of Fresno County. As our first field trial, it taught us many lessons about how to successfully run a sterile insect technique (SIT) program. Publication of the results from this field study marks a critical point in the evolution of the Debug project. We now have clear, peer-reviewed evidence that Debug technology can be used to massively suppress the number of biting female Aedes aegypti by automating both mass-rearing and release of sterile male mosquitoes. More than 2 billion people are at risk of contracting Aedes-borne viruses such as dengue, Zika, and chikungunya, and the global distribution of Aedes aegypti continues to expand worldwide. Our results give hope that we—in collaboration with forward-thinking partners—can turn the tide in this ongoing global health challenge. We have already incorporated what we learned from this trial into our other programs around the world, including our work with The National Environment Agency (NEA) in Singapore, and look forward to expanding to additional communities that routinely suffer from outbreaks of Aedes-transmitted diseases.





Jacob Crawford, PhD, Sr. Scientist, Verily and Brad White, PhD, Debug Lead Scientist, Verily

“A few years ago I could not even walk to my mailbox without getting several bites on my legs…This year I have only received one bite all summer… Thank you from a happy Clovis resident.” -B.B., Oct 17, 2019
“A few years ago I could not even walk to my mailbox without getting several bites on my legs…This year I have only received one bite all summer… Thank you from a happy Clovis resident.” -B.B., Oct 17, 2019


Debug Fresno, the largest U.S. release of male mosquitoes carrying Wolbachia, launched in 2017. Using an approach known as the Sterile Insect Technique (SIT), Debug Fresno released male Aedes aegypti mosquitoes, made effectively sterile by carrying Wolbachia, over 222 acres of residential neighborhoods in 2017. Our aim was to suppress the wild population of Aedes aegypti, which is invasive to California and has the potential to spread diseases, such as Zika and dengue. We continued the study during Fresno County’s 2018 and 2019 mosquito seasons, increasing our area almost 8-fold and adjusting our technologies to be even more efficient and effective. This past October we completed our final year of Debug Fresno with three seasons of strong suppression while gaining invaluable experience for scaling mosquito SIT around the globe.

Members of the Debug team in our larval rearing robot.




Nearly half of all humans are at risk of contracting diseases transmitted by the mosquito Aedes aegypti, and in 2019, many regions around the globe experienced a dramatic increase in dengue—reaching epidemic levels in some cases. Traditional approaches to controlling Aedes aegypti have not been sufficient to halt its spread. Mosquito SIT has the potential to dramatically reduce the incidence of disease spread by Aedes aegypti, while precisely targeting just this one species of mosquito.

Researchers have been developing mosquito-targeted SIT protocols and technology for more than a half century. However, most efforts have been limited by their inability to consistently produce healthy male mosquitoes on an industrial scale and efficiently remove biting female mosquitoes prior to release. In 2015, Debug by Verily began to develop technology to address these issues, including a highly controlled mosquito rearing system and precise sex-sorting systems. Field testing under realistic conditions is a critical step in the development of any new technology, so we were fortunate to form our partnership with the Consolidated Mosquito Abatement District (CMAD) and MosquitoMate, who were already studying this approach in the Fresno County area. Together, we made Debug Fresno a reality.

The Debug Fresno program design was fairly simple. With our partners, we chose several neighborhoods in the Fresno/Clovis metropolitan area where invasive Aedes aegypti had become widely established. We reared and released sterile, male Aedes aegypti, which cannot bite, into some of these areas to mate with local, wild female Aedes aegypti. If SIT were to work, we would see a considerable difference in the population of this mosquito between release and non-release neighborhoods. And, this is exactly what happened. At peak mosquito season, Debug Fresno observed decreases of biting, female Aedes aegypti in our release neighborhoods by up to 68% in 2017, 95% in 2018, and 84% in 2019.

While Debug Fresno may be conceptually straightforward, it was a significant operational and technical challenge. We measured impact in the field using a network of mosquito traps deployed at more than 2,000 locations by our partners at CMAD over the three years, who checked these traps 54,648 times, counted 1,569,589 Aedes aegypti, and in the process provided unparalleled insight into wild mosquito population dynamics. In South San Francisco, the Debug lab continued to grow and optimize. We reared a tremendous number of mosquitoes, converting approximately 1,100 pounds of larval diet into adult mosquitoes, while constantly improving the efficiency of our larval rearing and sex sorting technology. In total, we released approximately 48 million sterile male mosquitoes over 431 days spanning 3 seasons in Fresno/Clovis—repeatedly adjusting our release numbers and schedule—to evaluate release strategies and learn how to achieve the strongest suppression.

Members of the CMAD and Verily teams at a Debug Fresno outreach event in 2017.




Each year, our collaboration learned something new that helped our approach evolve. This year, our goal was to maintain strong rates of suppression in our 2018 areas, while continuing to expand into new neighborhoods. This year also turned out to be a record year for Aedes aegypti in California with a significantly earlier increase in density in Fresno County and detection in new cities. Even under these conditions, we maintained strong suppression in our 2018 release areas until late July when migration from untreated areas increased substantially. After adjusting and focusing our release strategies to accommodate the increased 2019 mosquito population, we achieved up to 84% suppression of biting, female Aedes aegypti. Results were stronger in some areas than others, which provided valuable data on minimum effective release rates under a range of scenarios. Our 2019 results also reinforced our perspective that starting as early in the season as possible, when mosquito populations are at their lowest, is the best strategy for achieving the maximum suppression with the lowest number of mosquitoes released.

As Verily’s first, and longest, field study has drawn to a close, we must take the time to express gratitude to our Debug Fresno partners, MosquitoMate and CMAD, and in particular to the technicians at CMAD whose hands-on work was critical to our success. We are also endlessly grateful to the residents of Fresno County for welcoming us and engaging in this study. Globally, interest in Wolbachia-based SIT is growing as scientists and governments look for effective and targeted ways to suppress the Aedes aegypti mosquito and reduce the diseases they spread. The experience and technological gains resulting from Debug Fresno have already been transferred to programs in other locations where this mosquito is both a nuisance and the cause of substantial disease burden. Debug’s progress on fighting the Aedes aegypti mosquito around the world continues, and we look forward to what is to come in 2020 and beyond.





Jacob Crawford, PhD, Senior Scientist, Verily and David Clarke, PhD, Factory Operations Manager, Verily

Good news is coming in from our field trial in Singapore. Last fall, we entered into a partnership with Singapore’s National Environment Agency (NEA) for the ongoing Project Wolbachia - Singapore to help reduce the population of ...
Good news is coming in from our field trial in Singapore. Last fall, we entered into a partnership with Singapore’s National Environment Agency (NEA) for the ongoing Project Wolbachia - Singapore to help reduce the population of Aedes aegypti. Over this past year we have been excited to see increasing suppression in our release areas as the program has grown to cover more residential blocks in the Tampines neighborhood of Singapore. As we close out the third phase of the field study and prepare to expand even further in Phase 4, we are happy to report that Project Wolbachia has achieved more than 90 percent suppression of the Aedes aegypti mosquito population in our release areas. Notably, in some of our release area blocks, we observed no female mosquitoes for multiple weeks at a time in the study traps.

Singapore’s high-rise and high density urban landscape presents a unique challenge to ensuring that the male mosquitoes we release are spread out effectively among different floors. For Phase 3, our collaboration treated 60 residential blocks, home to more than 22,000 residents, in Tampines West. We also deployed our mosquito sex-sorting technology, which has been successfully used in Debug Fresno and Debug Innisfail, to separate male and female mosquitoes using a computer vision algorithm and artificial intelligence.

16-story residential block 816 at the Tampines West release site under the Phase 3 and 4 phase study



As with all of our programs to date, we use a Wolbachia-based sterile insect technique. The male mosquitoes we release carry the bacterium Wolbachia and mate with urban female Aedes aegypti mosquitoes, that don’t have the bacterium. The resulting eggs from these matings do not hatch. Over time, the continued releases of sterile male mosquitoes, which cannot bite, gradually brings down the population of female Aedes aegypti, which can bite and spread diseases such as dengue and Zika. The NEA is exploring whether this mosquito population reduction can lower the risks of dengue transmission, which is a critical health issue in Singapore.

The Debug team will continue to carry out releases in an expanded release site in Tampines West in the next phase of the Project Wolbachia field study (Phase 4) in collaboration with the NEA. The expansion will double the release residential blocks to 121 and cover approximately 45,000 residents.

Map of Tampines West study site: green area = Phase 3 , dotted line area = Phase 4. Map provided by National Environment Agency.



We look forward to learning more about the effectiveness of continued release of sterile male Aedes aegypti mosquitoes through the expanded study site, as well as improving processes and release strategies in order to test new and innovative approaches to sustain a low Aedes aegypti population.




Yanni Yoong, Program Manager and Evdoxia Kakani, PhD, Senior Scientist, Verily