UCSD - University of California - San Diego

08/11/2026 | Press release | Distributed by Public on 08/11/2026 10:27

As New World Screwworm Returns to the U.S., UC San Diego and San Diego County Team Up to Track Risks

Published Date

August 11, 2026

Article Content

Key Takeaways

  • UC San Diego and San Diego County partnered to build a real-time New World screwworm risk-tracking dashboard for public health officials.
  • The tool combines detection reports, environmental data and media coverage to flag risk county by county.
  • The partnership offers a model for how university researchers and health agencies can team up to respond quickly to emerging threats.
  • Officials say the dashboard helps them gauge how urgently to prepare as the outbreak nears California.

In the 1950s, the New World screwworm cost U.S. livestock producers tens of millions of dollars a year, as much as $50 to $100 million annually in the hardest-hit Southwest, before it was eradicated from the United States and pushed south to Panama. Now the flesh-eating pest has spread north again, reaching Texas and New Mexico and threatening livestock, wildlife and even people.

To help local officials stay ahead of the threat, the County of San Diego Health and Human Services Agency (HHSA) Public Health Services and University of California San Diego researchers developed a tool to help track the screwworm, a parasitic fly whose larvae feed on living tissue.

"Our County public health partners alerted us to the need for better situational awareness of New World screwworm," said Eliah Aronoff-Spencer, MD, PhD, professor of medicine at UC San Diego School of Medicine and affiliate member of the UC San Diego Design Lab and Qualcomm Institute. "We built a dashboard to generate regional risk profiles. This is just one example of how we are responding to County needs with a focus on real-world issues. It's a model that has brought us great success, like the Tijuana River Crisis Environmental Dashboard."

The new dashboard combines reports of confirmed detections, environmental suitability for the fly and its larvae, and media coverage to estimate risk nationwide on a county-by-county level. The dashboard is currently available only to project partners and public health officials, although the team ultimately hopes to make a public version available.

Seema Shah, MD, MPH, who is medical director of the Epidemiology and Immunization Services Branch for the County of San Diego's Public Health Services Department, noted the incorporation of news articles was one of the dashboard's innovations. "Traditional reporting mechanisms for public health are often delayed," she said. "Lab confirmation can take days or weeks. By incorporating media reports, we can identify potential threats sooner and stay one step ahead."

"The tool gives you a sense of where you might expect to see cases next," added Mark Beatty, MD, MPH, the assistant medical director for the County's Epidemiology and Immunization Services Branch. "That's helpful in determining how we should be preparing. Is the threat imminent, or do we have six months? We're in a very concerning phase right now, and the tool backs that up."

Why the screwworm is different

Unlike most fly larvae, which feed on dead or decaying tissue, New World screwworm larvae burrow into living flesh. The female fly lays her eggs in open wounds or natural body openings, and once the larvae hatch, they feed on healthy tissue, causing wounds to grow larger and deeper, and leaving them vulnerable to secondary infections. Left untreated, infestations can severely injure or even kill livestock and wildlife.

Although cases are uncommon, humans can also become infected; however, unlike infectious diseases such as COVID-19, New World screwworm does not spread from person to person. The larvae invades wounds or mucous membranes, requiring prompt medical treatment to remove them and prevent further tissue damage.

Cochliomyia hominivorax, the New World screwworm fly, causes injury or death to livestock and wildlife by laying eggs in open wounds or natural body openings. Once the larvae hatch, they feed on healthy tissue. Credit: iStock/Lidya Elfa Sari

The geographical expansion of the pest has been facilitated not only by the fly's natural ability to travel miles looking for hosts, but also the movement of livestock, pets and birds and other wildlife.

"We knew in 2023 that New World screwworm was going to move northward, but I wasn't expecting it to move as fast as it has," said Beatty. "Although the source of the infections in the U.S. is still under investigation, the fact that it's in the U.S. is 100% clear.

"Once it entered Texas, we quickly saw an increase in detections," he continued. "It's in a place where it used to live, so it's not surprising it's taking a hold again."

Fighting back

In the 1950s, the New World screwworm was eliminated from the United States using one of the most successful biological control campaigns ever attempted. Called the sterile insect technique, the approach used the mass release of radiation-sterilized insects into the wild to cause reproductive failure and population collapse.

Officials today are drawing on a similar strategy. Led by the U.S. Department of Agriculture (USDA), the latest eradication effort has reintroduced the technique, combined with pesticides and animal movement quarantines. U.S. Environmental Protection Agency approval is also being sought for a genetically modified all-male strain, which is now in field testing. Researchers at UC San Diego are also developing next-generation genetic technologies that could strengthen future screwworm control and eradication efforts. (See related story, "Flesh-eating Screwworms Have Returned. Which New Technologies Could Stop Them?")

"We are working closely with the California Department of Food and Agriculture to connect local veterinarians with screwworm resources for surveillance in our region," said Emily Trumbull, DVM, veterinarian and lead for the Epidemiology Unit's One Health Program. "The flies can affect any warm-blooded animal, so working together with veterinarians serving livestock, pets and wildlife is critical for identifying suspect cases and preventing cases in people. The dashboard takes into account environmental factors that can help us understand how the risk to our local region is changing before the fly arrives. That's why the dashboard is valuable."

A New Model for Public Health Response

The screwworm dashboard is the latest project from Resilient Shield, a UC San Diego initiative and U.S. Centers for Disease Control (CDC)-funded center led by Aronoff-Spencer and co-PIs. As one of 13 core facilities in the CDC's new Insight Net, a national outbreak and disease modeling network, Resilient Shield is helping pioneer a new approach to building public health tools - one driven by the needs of public health professionals.

"In public health, we always know our most urgent priorities, but too often we don't have the immediate resources or in-house technical solutions to achieve them," said Shah. "The screwworm is a perfect example. It is a critical threat, but it is an issue our academic partners might never have prioritized without our direct ticket. This partnership solves our immediate problem while providing shareable, open reference designs that demonstrate exactly how public health, academia, and industry can successfully work together."

Instead of researchers guessing what agencies need, organizations facing real-world threats can submit tickets to Resilient Shield for the solutions they require. In addition to San Diego County, Resilient Shield's partners range from the California Department of Public Health to the Navajo Nation and the broader Insight Net.

This multidisciplinary model allows for rapid, cross-institutional mobilization. The center's very first ticket was a flu tracking request also issued by Shah; the response was co-led by Resilient Shield co-PI Ruy Ribeiro at Los Alamos National Laboratory. For the current screwworm threat, the response was a direct collaboration between Aronoff-Spencer and mathematical epidemiologist Natasha Martin, DPhil, professor medicine and vice chief in the Division of Infectious Diseases and Global Public Health at UC San Diego School of Medicine.

To answer those requests, Resilient Shield has engineered a modular, scalable resource hub. Working alongside technology partners like Google and MITRE, the center integrates broad data systems, cross-referencing human disease, livestock, environmental and weather data, national health records, and social listening. When a ticket comes in, the team can rapidly assemble the required tools from the open hub. This allows the team to deploy whatever is needed, whether that requires public-facing web and social media, secure compute, robust simulation engines, or AI agent builders.

"Our central innovation is the true convergence of partner priorities with scalable engineering," said Aronoff-Spencer. "We do not build in a vacuum. Our infrastructure is built directly on the priorities dictated by our partners. In addition, because our platform is built on an open, modular architecture, every solution we develop strengthens the system and makes it more adaptable for the next public health challenge."

Learn more by visiting the Resilient Shield, County of San Diego Public Health Services or USDA Stop Screwworm Hub websites.

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UCSD - University of California - San Diego published this content on August 11, 2026, and is solely responsible for the information contained herein. Distributed via Public Technologies (PUBT), unedited and unaltered, on August 11, 2026 at 16:27 UTC. If you believe the information included in the content is inaccurate or outdated and requires editing or removal, please contact us at [email protected]