Can Your Phone Tell You if You've Been Exposed to COVID-19?

In Alabama, the app is called GuideSafe. In New York, it’s the COVID Alert NY. In Wyoming, it’s called the Care19 Alert.

The kind of information that the apps offer also varies, but the basic principle is the same. For example, if you get a notice in New York — usually a phone call — that you tested positive, you'll also get a code from the health department that you then can enter into the app to send the information anonymously to anyone you might have been near.

While the app works best when you leave it running in the background on your phone, you don't have to leave the app on all the time. You can turn it off and on whenever you want.

As of Dec. 16, at least 22 states, the District of Columbia and two U.S. territories were using contact tracing apps, mostly based on the Apple-Google technology: Alabama, Arizona (phased rollout across the state), California, Colorado, Connecticut, Delaware, the District of Columbia, Hawaii, Maryland, Michigan, Minnesota, Nevada, New Jersey, New York, North Carolina, North Dakota, Oregon (phased rollout with statewide availability expected in January), Pennsylvania, Rhode Island, South Dakota, Virginia, Washington state and Wyoming, plus Guam and Puerto Rico. (On iPhones, Colorado, Connecticut, the District of Columbia, Maryland and Washington state have enabled an opt-in to Exposure Notifications in the phones’ device settings but have no separate app.) And in the absence of statewide apps, Georgia Tech, the University of Illinois Urbana-Champaign and the City of Santa Fe in New Mexico are using apps in their communities.

A Massachusetts app is on track to be developed. Oklahoma expected its app to be rolled out in November, but it has not been released yet. Wisconsin’s app is expected to come out later in December.

South Carolina’s health department initially committed to creating an app for its state — SC Safer Together available in both the Apple App Store and on Google Play — but state legislators blocked the state health department and other state agencies from using cellphone apps for contact tracing because of lawmakers’ security and privacy concerns. Utah debuted its own app in April but turned off its Bluetooth and GPS location tracking by July.

Will it work everywhere?

If you travel outside of your state usinyour local COVID tracing app, it may work in coordination with some other nearby state apps. For example, apps from New Jersey, New York and Pennsylvania are compatible with each other.

So New Yorkers will get alerts if they travel to one of those states or if someone from one of those states travels to New York and exposes them. However, different companies have created many of the apps scheduled to debut and won't necessarily trade information with other state-supported apps.

Some critics worry that these apps may create a false sense of security and emphasized that a lot of people have to opt in for them to be effective. In California, 4 million users downloaded and signed up for CA Notify on Dec. 10– 11, its first two days available, but officials need a lot more of the state’s 39.5 million residents to say yes for it to work well, according to the California Department of Public Health.

And epidemiologists, such as researchers at Oxford University, say that while having 60 percent of people using an app would be ideal, only a small percentage of smartphone owners would have to join to give health departments information about new hot spots. More important: The researchers point out that at least one infection — and, therefore, one possible death — would be averted for every one to two people who opt to use the software. So a few thousand users could save thousands of lives.

Is this a flawless system?

The underlying Apple/Google technology has had hiccups in some countries, such as England and Wales, where apparent alerts that seemed to indicate a person was exposed to someone with COVID-19 and should self-isolate were sent out. But the messages had been intended only to indicate the app was working properly.

Furthermore, some concerns over privacy led to recommendations from police departments in the United Kingdom that officers do not download the COVID app to their work phones. Since then, police there are being told to use the app on their personal smartphones instead.

Some copycat apps also have popped up online. The best practice is to stick only with smartphone apps that use the Exposure Notification System and that your local health department supports. If you see conflicting information online — don't trust user reviews — contact your local health department for confirmation.

As with any technology, contact tracing using a smartphone app could help make you safer. But you'll still have to be vigilant by wearing a face mask, staying at least 6 feet from others and routinely washing your hands.

Editor's Note: This article was originally published on November 9, 2020 and is now updated with new information on coronavirus exposure apps.