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