Apple and Google plan to directly integrate contact-tracing software into smartphones as they aim to broaden a jointly developed initiative to combat the coronavirus.

The technology, first launched in April on Apple's iOS software and Google's Android system, is meant to alert people through their smartphones when they come into contact with a person infected by the coronavirus.

However adoption has been slow in the United States, with only a handful of states building smartphone apps that work with the system.

Under the change, public health authorities will be able to use the company's program without building their own apps, and people who sign up for the service will not need to download a separate stand-alone app to use the system.

"As the next step in our work with public health authorities on Exposure Notifications, we are making it easier and faster for them to use the Exposure Notifications System without the need for them to build and maintain an app," Apple and Google said.

Apple and Google have emphasized that the program protects user privacy and requires participants to opt-in in jurisdictions where the system is employed.

"Exposure Notifications Express provides another option for public health authorities to supplement their existing contact tracing operations with technology without compromising on the project's core tenets of user privacy and security," Apple and Google said.

"We are committed to supporting public health authorities that have deployed or are building custom apps."