Bringing COVID-19 exposure notification to the public health community

Bringing COVID-19 exposure notification to the public health community

Starting in 2006 with the Public Health Laboratory Interoperability Project (PHLIP)—one of the first systems that allowed public health entities to exchange standardized data—APHL has worked to make connections between public health laboratories and agencies more efficient. Those efforts took a dramatic step forward with the APHL Informatics Messaging Services (AIMS) platform, which has evolved from a one-way router of critical health information to a secure, cloud-based platform that transports, translates, validates and hosts data for federal, state and local public health agencies.

 The emergence of COVID-19 required swift action to develop systems and processes that support public health agencies and their pandemic response efforts. In the last seven months, APHL has worked to create new connections, develop new message formats, standardize language and host a variety of solutions to aid in the COVID response. This blog post, regarding exposure notification, is the first in a series that outlines and explains these efforts.

How Does Exposure Notification Work?

To limit the spread of COVID-19, information must travel faster than the virus can. The scope and transmission rate of COVID-19 makes this a monumental challenge for public health agencies. Exposure notification technology, however, is a potential game changer. By providing rapid alerts to individuals who may have been in close proximity to someone who has COVID-19, exposure notifications allow the spread of information to stay one step ahead.

Working in conjunction with Apple, Google and Microsoft, APHL is taking a major step to support public health agencies that want to provide focused, privacy-preserving and user-controlled exposure notifications at scale using the Apple | Google Exposure Notifications System. APHL’s presence on the project gives the US public health community a capable and accountable partner for hosting key components of this groundbreaking technology.

The Apple | Google Exposure Notifications System (A|G ENS)

To augment traditional COVID-19 contact tracing efforts around the world, Apple and Google co-developed the A|G ENS, which consists of an Exposure Notification Application Protocol Interface (API) that is available on both the iOS and Android operating systems. Apps developed by public health agencies can then use the Exposure Notification API to help determine if a user may have been exposed to another user who subsequently tested positive for COVID-19. This is accomplished through the use of privacy-preserving randomly generated numbers also known as keys, which in turn generate temporary IDs that are transmitted between devices using Bluetooth Low Energy signals. Apps using this system are not permitted to collect or use location data from the device, and user identities are not revealed to other users, Apple, Google or APHL.

Rather than each state and territorial public health agency bearing the burden of building and hosting its own key servers, a national server can securely host the keys of those affected users, eliminate duplication and enable notifications across state borders. APHL is also championing the effort to build and host a national key server on behalf of the public health community. This will allow users to continually benefit from exposure notifications as they travel across state lines, and help state and territorial agencies deploy their apps quickly.

“APHL’s participation is key to the success of these efforts,” said Washington State Secretary of Health John Wiesman. “Without a national key server, each state that chooses to implement such an application would be responsible for its own data sets. APHL’s centralized and secure national server will be accessible to every state public health agency.”

Microsoft is supporting the partnership by working with APHL to host the national key server, based on the open source reference design created by Google Cloud. Through Microsoft’s Azure cloud platform, Microsoft will provide cloud services that will allow APHL to host the key server and securely enable interstate operability for the apps that public health agencies deploy.

Only users who choose to download an app developed by their public health agency and voluntarily opt in can receive exposure notifications. If users are alerted to a possible exposure, the app will also provide information about what to do next.

“We’re honored to partner with Apple, Google and Microsoft to make this groundbreaking technology accessible to state and territorial public health agencies,” Bill Whitmar, president of APHL and director of the Missouri State Public Health Laboratory, said. “Apps using this technology will rapidly inform users of a potential exposure to COVID-19 and provide them information they can use to protect themselves and their families.”

APHL develops technological innovations that support public health agencies at the federal, state and local level. For more information on how your agency can benefit from a partnership with APHL, contact


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