Covid Watch

More from Covid Watch

By Covid Watch
on September 18, 2020

How testing Covid Watch led to the most sophisticated exposure notification app available anywhere– a digital tool capable of fighting the pandemic in more ways than one.

Contact tracing and isolation of persons exposed to confirmed cases of COVID-19 are pillars of transmission reduction strategies, but living in the Information Age has allowed us to augment these tried and true efforts with digitized tools. The founders of Covid Watch pioneered the development of anonymous exposure notification technology that privately notifies individuals when someone who has been within their Bluetooth range for a specific amount of time has a confirmed infection. This privacy-preserving protocol is designed to accelerate and augment manual contact tracing and is the basis for the Covid Watch app and other apps built using the Google-Apple Exposure Notification (GAEN) API.

Though other exposure notification apps have been released, with more still in development, Covid Watch does more than just warn you of possible exposure–it is the only app that incorporates advanced algorithms to account for your actual risk of contracting COVID-19. We have an advanced risk model that lets us notify users who are the highest risk to others, and our dynamic quarantine recommendation eliminates unnecessary hardship. By individualizing the exposures, Covid Watch can target those in high-risk areas and help to avoid large-scale lockdowns. For example, a blanket fourteen day quarantine is too broad of a recommendation for everyone; some exposures may pose almost no threat of infection, and a disproportionate quarantine recommendation can cause undue stress, financial or otherwise, for many. These unique built-in features make Covid Watch an effective tool for not only protecting our health and privacy, but also in aiding the responsible reopening of communities.

For those of us who don’t wear a lab coat to work, it may be difficult to understand how the same technology that connects our playlist to our portable speakers can also determine if we’ve been exposed to a harmful virus. So, how did we build the most sophisticated exposure notification app available? For starters, extensive research and a lot of testing … and we didn’t do it alone.

Thanks to our partnership with the University of Arizona, one of the top public research institutions in the country, Covid Watch underwent rigorous testing over the course of several weeks this summer, fine-tuning with original research everything from the signal strength calibration to the dynamic risk scoring model developed by Dr. Joanna Masel from the university’s Department of Ecology and Evolutionary Biology. In collaboration with Covid Watch and University of Arizona colleagues, Dr. Masel developed a method to calculate the level of exposure risk of each Bluetooth interaction by measuring the length of exposure to and distance from a person with a verified diagnosis, as well as at what point during the person’s infection a user was exposed. The level of danger of each individual exposure is calculated and assigned a risk score which is then used to inform quarantine recommendations. The entire preprint is available on medRxiv for those interested in reading more of the research.


During a recent interview on NPR, Dr. Masel helped explain the risk scoring model, saying “So we've developed a new way of really getting a hold of how dangerous different interactions are. In general, you are most likely to pass on COVID right around the time that your symptoms start. That first day when you're ever so slightly under the weather, and you're not even sure whether you're sick yet - that must be the day that you pose the most risk to others. Five days in when you feel terrible, you might be actually much less danger to other people. So we quantify that. And we combine that information to figure out how dangerous it was.”

Accurate identification of exposures is critical to identify the people that need to isolate and for the duration that they need to isolate. Exposure is assumed to occur when one individual inhales the air that the other has exhaled. For this reason, a critical risk factor is whether the individuals are face-to-face, such that the transmitter is breathing in the direction of the receiver. Face-to-face interaction, not just contact within a certain distance, is part of the WHO definition of a contact. We conducted a series of experiments designed to align the exposure risk formula in Covid Watch with the WHO’s definition of a “contact” – being in face-to-face contact within one meter of an infected person for 15 minutes or more OR in direct contact for any duration. 


A series of tests were designed to ensure that exposure notifications were functioning as expected in an environment where users are moving about and coming into contact with each other as they would in their daily lives. Using devices of different generations and operating systems, hundreds of various real-life scenarios were mimicked by changing the position and orientation of the devices, including signal strength change between walls and floors. The results of the alpha test helped tune the parameters of exposure notifications within the Covid Watch app.

Our research-based approach to development allowed us to launch a one-of-a-kind, fully calibrated app ready for wide adoption. In its inception Covid Watch was built to help slow the spread of Covid-19 while protecting digital privacy; but through innovation with a trusted research partner, it’s now more than an exposure notification app–it’s a tool to fight the whole pandemic.
By Covid Watch
on August 19, 2020
Available now in the App Store and Google Play, the first-ever exposure notification app using an evidence-based dynamic risk model begins a phased rollout at the University of Arizona and distinguishes itself from competing platforms in the process.
Believe it or not, fall is just around the corner and many college students across the country are already hitting the books. Those who are not taking all of their classes online, and spending their entire semester on Zoom, will be back in classrooms in just a few days. While most states have been tirelessly planning a safe homecoming for their campus communities, Arizona doubled down and emerged as the leader in the back-to-school fight against COVID-19. As the first in the nation to deploy Covid Watch – the exposure notification app co-developed, tested, and validated by one of its most prestigious research universities, the Grand Canyon State is paving the way for the rest of the nation’s campuses to reopen as safely as possible.

The University of Arizona (UArizona), ranked one of the top 15 public research universities in the nation, launched the Covid Watch Arizona app for university students, faculty and staff after several weeks of rigorous testing, with the app now available for free download on the App Store and Google Play. Though not mandatory for the UArizona community, it is the first exposure notification app to be adopted by a higher learning institution in the U.S., and because of its fully customizable capabilities, it’s tailored to UArizona Wildcats every step of the way. Most importantly though, the launch marks the introduction of the first app to use a unique evidence-based dynamic risk model with real-time recommendations to help people make informed decisions on how they can help slow the spread of COVID-19. This campus-wide launch will help demonstrate success and identify best practices that can help guide the phased rollout to state-wide adoption. We are ready to expand to other regions within Arizona and beyond - and we’re excited to prove it.

Covid_Watch_App_Insta_Story_3 Covid_Watch_App_Insta_Story_7 Covid_Watch_App_Insta_Story_4

UArizona is encouraging students, faculty and staff returning to campus to download the Covid Watch App through an engaging digital outreach campaign on social media.


The university exhibited their commitment to preserving privacy by co-developing with Covid Watch one of the first fully anonymous exposure notification apps built on the Google Apple Exposure Notification (GAEN) API in the United States, but it was their dedication to research that helped us create the most sophisticated exposure app available anywhere. Unlike some recently unveiled solutions that are only now formulating data on certain simulated scenarios, the Covid Watch app has been undergoing extensive testing throughout the UArizona partnership. Everything from the app’s signal strength calibration to the dynamic risk scoring model has been fine-tuned through original research. 

The first-of-its-kind risk model was built based on studies conducted by Dr. Joanna Masel from the University of Arizona Department of Ecology and Evolutionary Biology. In collaboration with Covid Watch and UArizona colleagues, Dr. Masel developed a method to calculate the level of exposure risk by assessing the duration of exposure to and distance from an infected person, as well as at what point during the infection a user was exposed. Covid Watch is the only app that actually uses this information to generate exposure notifications and individualized public health recommendations that better reflect real life interactions.
This built-in risk model is also a design element that aids the Covid Watch app’s readiness for wider deployment. It allows for easier regional calibration because it is customizable to the corresponding local public health authority’s current recommended precautions; exposed users will be offered region-specific resources upon notification, as well as information on public health guidelines determined by the area.

UArizona-Covid-Watch-App-Field-TestsUArizona has been testing the Covid Watch App in real-world scenarios on campus since July.
Having this platform approach versus a bespoke solution for each individual state is incredibly valuable, especially in a country the size of the U.S. where many people live long distances from their friends and families, often in different states. The Covid Watch Platform’s global interoperability would allow an Arizona student going home to California for the weekend to select and change their region with ease, and return back to campus again, once the laundry’s all done. The same app and the same data will be interpreted through the lens of the updated region; no potential exposures are lost or blocked, providing the user with peace of mind that their health or the health of others will not be compromised simply by traveling outside the app’s reach. 

The University of Arizona chose the Covid Watch Platform because its exposure notification system utilizes a fully anonymous, privacy-preserving algorithm paired with a verification portal designed for public health officials to confirm positive cases of COVID-19. Through our collaboration, we designed an app with the capability to take this technology far beyond the Tucson campus community. 

The barrier to entry for other states to follow is that much smaller now that Arizona is one of the first states in the U.S. to deploy an exposure notification app built and published on the Google-Apple APIs. Covid Watch is ready to launch in any jurisdiction globally, once approved by a state or federal public health authority. Contact the Covid Watch Partnerships team for additional information on our four-week roll out plan.

The Covid Watch nonprofit organization began in February 2020 as a volunteer-led initiative to create public health technology to slow the spread of COVID-19 while preserving digital privacy rights. We are now a team of more than 650 volunteers from around the world with a collective vision of ending this pandemic without sacrificing our civil liberties.

Our original mission is still the same, and as the pioneers of the anonymous protocols that led to the development of exposure notification technology, we have a strong commitment to innovation and making this digital health tool available to those who need it most. We value altruism and transparency; therefore, our solutions are built on open source code that is available for all to see. We continue to invest in adjacent areas like hardware integration, privacy-preserving systems for the identification of hot-spots, and wearables to expand the reach of exposure notifications beyond smartphones – and as always, we continue to empower communities to fight the pandemic while protecting digital privacy.

If you are a representative of a state or federal public health authority and interested in bringing the Covid Watch exposure notification platform to your community, please reach out to us through our website to schedule a consultation.
By Covid Watch
on July 21, 2020


Against the backdrop of rising COVID-19 cases and hospitalizations nationwide, the start of the school year is quickly approaching — and universities are faced with the high-stakes decision of if and how they are going to bring students back to campus. Many are looking to technology solutions that can help stop the spread of coronavirus and empower communities to return safely to their daily lives. Covid Watch has built one such tool — a fully anonymous exposure notification app that notifies community members of potential COVID-19 exposure while protecting their privacy.Last month, Arizona became the first state to begin testing the Covid Watch app through a pilot at the University of Arizona. Home to roughly 60,000 students, faculty, and staff, the Tucson-based university, like nearly every other in the country, has been working continuously on the Herculean task of planning a safe reentry strategy for its bustling campus.

“Our faculty and other researchers continue to step up and find new solutions to this complicated health care issue,” said University of Arizona President Robert C. Robbins in a report from the university. “Each solution provides another piece of our reentry strategy, and I am proud our faculty are the first to test this app.”

After Arizona Governor Doug Ducey granted approval for the pilot, the University of Arizona Campus Reentry Task Force then seamlessly integrated testing of the Covid Watch app, in addition to traditional manual contact tracing and self-reporting, as part of the university’s three-tiered “Test, Trace and Treat” program. This multi-layered plan to slow the spread of COVID-19 in their community will also include diagnostic testing, antibody testing, and treatment of those who may have been infected, or have tested positive, for COVID-19.
Covid Watch and the State of Arizona were a natural fit for the first pilot testing partnership; together, they are leading the privacy-first approach in their mutual commitment to never collect personally identifying information. Other states have developed apps based on digital contact tracing that collect personal data, such as contact information or GPS location, like Utah’s Healthy Together and North Dakota’s Care19. Such apps are either for-profit or have been caught mishandling user data and have been called out by privacy groups like the ACLU and EFF, suffering low adoption rates as a result.
Covid Watch can’t mishandle your data because it doesn’t collect any, and as far as privacy goes–it’s inherent to the design–and its mission is shared with the ACLU and EFF. The Covid Watch app is a non-profit, novel technology that builds a fully anonymous app on top of the Google/Apple Exposure Notification (GAEN) APIs. The app provides exposure notification alerts to persons who may have been exposed to COVID-19 by using Bluetooth technology to share signals between app users who have come in contact with one another. Think of it as a handshake of sorts — a quick hello, just between phones.
By Covid Watch
on July 17, 2020
Without social distancing, quarantine, or other measures, a virus like COVID-19 can spread rapidly through the population. COVID-19 spreads most easily between people within close distances via droplets in the air created while coughing, sneezing, or talking. People can become contagious before their symptoms appear, or they may never develop symptoms, so it is possible to transmit the disease without a person realizing they are infected. If the virus is allowed to spread too quickly, it can overwhelm the capacity of healthcare services, resulting in less access to treatment and a higher rate of deaths.

Wearing a mask is a great way to slow transmission and save lives, but masks alone cannot prevent every case. Personal protective equipment can be prone to human error or inconsistent use, and it is less effective when people are in close contact over a long period of time.

How Widespread Quarantine Works

The quickest way to slow the spread of the virus is a universal quarantine, where everyone stays isolated regardless of their infection status. While this stops the virus in its tracks, a full quarantine is difficult to maintain over a long period of time, since people still need access to food and medicine, and other essential services. Lifting a quarantine too soon without additional measures in place comes with the risk of a second wave of infections, as we are currently seeing in many countries around the world. Some countries have responded to their second wave with geographically restricted or partial quarantines in “hot-spot” areas.

Complete quarantines, where everyone in a geographic area stays isolated regardless of their infection status, can stop the spread of COVID-19 in its tracks. However, this can be difficult to maintain over the long term without major disruptions to essential services and economic activity.

How Manual Contact Tracing Works

A second effective measure for slowing the spread of the virus is contact tracing, which works by having potentially infected people, who have been identified by patient interviews and outreach to their circle of contacts, isolate themselves during the time they are contagious. It is similar to the partial quarantine described above, but is more targeted towards the people who are suspected of being infected.
Traditionally, this method works by having contact tracers interview every known infected person, then follow up with all their recent contacts, who go into quarantine to avoid spreading the virus. However, this method requires the infected person to know and remember the people who they had contact with over the past couple weeks.
Being a contact tracer is very time-intensive work, not unlike being a detective. Think back. Would you be able to remember every cashier you interacted with over a two week period? Or know who stood next to you in line? As a result, contact tracing becomes less effective when there is a high number of cases, simply due to the lack of infinite time and resources.
Contact tracing operations also face some unique challenges in the United States. First, many people in the US don’t answer calls from unknown numbers, so manual contact tracers often struggle to reach contacts of infected individuals. Second, while many people altruistically participate in the process and help contact tracers, some find the process invasive of their privacy and hesitate to share this information with authorities.

Covid Watch Blog Post - Medium Post 3-3Contact tracing allows for a smarter, more targeted quarantine, where only those who came into contact with an infected person are required to isolate themselves. However, it can be very difficult to discover and notify every person who may have been exposed.

How Exposure Notification Apps Can Help

To supplement manual contact tracing, new contact tracing apps have been developed to automate the process. While these apps have been shown to be effective in slowing the spread of COVID-19, many of them also come at the expense of personal privacy. This is particularly true for apps that use GPS location data, which can also be a security risk for many users. It also can result in an over-collection of data for many individuals who may have been near the infected person, but not necessarily in direct contact.
Enter Covid Watch, an exposure alert app that allows contacts to be notified anonymously of exposure, rather than being identified, tracked or traced. It helps notify people more quickly if they may have been infected, who otherwise might fall through the cracks of manual contact tracing. Covid Watch eliminates the need for an infected person to remember every single person they interacted with, since their mobile device can anonymously remember other anonymous mobile devices it was near over the most recent two-week period. Less dependence on traditional manual detective work means the system can work well even when there are very high numbers of cases.
In other words, Covid Watch allows information to travel faster than the virus on a large scale. It empowers people to take action, whether to isolate themselves, or to notify their network as soon as they become aware that they pose a risk to their circle of contacts. Covid Watch does not replace or expand manual contact tracing, but instead works with crowd-sourced information to rapidly inform you about your own health status or that of your community, while totally protecting everyone’s privacy.
The Covid Watch app allows people to receive completely private notifications on their phone whenever they may have been in contact with a contagious person. This new automated system can help reach people who would have fallen through the cracks of traditional contact tracing. With information from the app, people can start to self-isolate even before their symptoms appear, preventing further spread of the virus.

Why Covid Watch?

By using Bluetooth instead of GPS, Covid Watch doesn’t need to collect any personal information. It works by sending anonymous codes between phones that have been within a close distance, which are later used to alert contacts.
If a person is confirmed to be infected, they can choose to send an anonymous alert via the app, which notifies everyone who was in close Bluetooth range with that person during their contagious time period. In addition, the app sends recommendations for further action specifically tailored to the timing of each person’s exposure and the Bluetooth signal strength during that exposure. Exposure information is also always stored locally.
Stay tuned for our upcoming blog post explaining how this technology can work while retaining the anonymity of app users, enabling your app to act like a Walkie Talkie, exchanging secret passwords with nearby phones that are later used to route alerts only your phone can interpret.
The open source technology used by Covid Watch empowers people to slow the spread of the virus without sacrificing their data security or privacy. Without buy-in from the public, no public health intervention can be effective, no matter how well-intentioned. In the case of Covid Watch, communities get the best of both worlds. Public health improves because people receive information about their exposure that they wouldn’t otherwise be aware of. And the public’s trust increases because the system is anonymous, ethical and transparent.
Covid Watch is now accepting applications from public health departments, governments, and universities for its pilot programs and statewide releases. To learn more, schedule a consultation.
Acknowledgement: This article was written in collaboration with Hello SciCom co-founders @carolynayers and @sarahrosesiskind. Hello SciCom helps scientists and tech entrepreneurs express complex ideas in a way that’s clear, accessible, and entertaining (especially great ideas like Covid Watch). Contributing editors from Covid Watch were Tina White, Jess Graeser, and Martin Lum.
By Covid Watch
on May 08, 2020
Emergent Ventures awarded Covid Watch $100,000 on Thursday to continue its work on an anonymous exposure alert app that protects privacy while quickly notifying users if they've been in contact with the coronavirus. 
The COVID-19 Prizes are given to individuals and organizations that have shown "significant success" crafting solutions during the current global pandemic. Recipients do not apply for the awards. 
"These funds will help us encourage adoption of our app, the most private way to alert people they've been exposed to COVID-19," said Tina White, executive director of Covid Watch. "We're excited to be recognized for our work to stop the virus and prevent a once-in-a-lifetime erosion of privacy norms." 
Emergent Ventures founder Tyler Cowen set aside $1 million for the COVID-19 Prizes earlier this year. The award comes via the Mercatus Center at George Mason University, where Cowen works as a professor of economics. 
“When it comes to fighting COVID-19, we don’t know where the critical advancements and breakthroughs are going to come from,” Cowen said. “These prizes are a way to incentivize innovation and help to repay those who work on this issue, as they are unlikely to receive anything close to the full social value of their efforts.” 
Covid Watch relies on a network of volunteers in the San Francisco Bay Area and around the world, including epidemiologists, public health experts, developers, lawyers and communications specialists. 
In just a few months, that team has built an app that offers anonymous and privacy-protecting alerts with plans to authenticate diagnoses by health officials interested in providing this service within their jurisdictions.