California residents get Covid exposure notifications via CA Notify

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California residents get notifications via CA Notify, a system that anonymously alerts users about their exposure to the coronavirus.

CA Notify is based on technology made by Apple and Google called exposure notifications. It utilizes Bluetooth to determine when people have been exposed to each other for extended periods of time, hinting at possible coronavirus transmission, without gathering personal information.


The app alerts users that they may have been exposed to the coronavirus early in a potential infection. With this, they will be able to get tested or quarantine before they spread the virus.

California’s Department of Public Health (CDPH), which runs CA Notify, states that it does not hold statistics about the number of activations. However, the department believes that 4 million Californians may have registered on the app of Friday, based on the number of access times a specific URL got. California has under 40 million residents, so it has covered about 10% of the state’s population to date.

CA Notify is considered the biggest practice for Exposure Notifications Express, an update to the Google-Apple framework launched in September that aims to improve adoption. Governments are able to inform users that the apps and systems are available in their area.


CA Notify can work on both iPhones and Android phones, although it needs a device that can operate up-to-date software. California explains that the app complements other public health protocols, such as wearing a mask, physical distancing, and hand washing. Exposure notifications are not the same as contact tracing, in which people are contacted by public health departments manually to detect those who may be at risk.

Contact tracing app

Another app developed during the pandemic is SafePass.

Users can activate the contact tracing app after downloading Citizen’s other app, called SafeTrace, which is used to summarize one’s Covid-19 health history. Citizen will send users at-home tests, and subsidize the cost if the contact tracing app shows they may have been exposed.


Meanwhile, if a user wants to get hold of an at-home test without an indication they have been exposed, they can purchase one for $140 through Citizen.

The SafePass tool is part of the Citizen app. It automatically reveals the results of the Covid-19 tests the company distributes and lets users upload other tests themselves.

When a user’s test is positive, the app automatically and anonymously informs other users they have been near. To protect users’ privacy, information on contact tracing and one’s health is anonymized, encrypted, and stored for only 30 days.

Citizen started with about 600,000 users in March 2020 and now serves over 5 million users. Citizen first gave users alerts from 911 data. The company’s analysts monitor and manage 911 communications that it uses to send out real-time updates. Citizen also has user-generated content and personal safety features.

Contact tracing apps function when two individuals have been in close proximity to one another for a long time. If someone has the virus, the app will send an alert to people they have been in close contact with.

Apple and Google’s platform aims to provide citizens more privacy but it does not give epidemiologists the entire data.

Germany, Italy and Denmark have abandoned their so-called “centralized” approach that processes data on a state-controlled server. They welcome Apple and Google’s “dencentralized” approach, where data is analyzed on the handset itself, thereby reducing privacy issues.