Apple, Google are building a virus-tracking system. Health officials say it will be practically useless.

Apple and Google’s announcement last month of a joint effort to track the coronavirus by smartphone sparked a wave of excitement among public health officials hoping the technology would help alert them to potential new infections and map the pandemic’s spread.

But as the tech giants have revealed more details, officials now say the software will be of little use. Due to strict rules imposed by the companies, the system will notify smartphone users if they’ve potentially come into contact with an infected person, but it won’t share any data with health officials or reveal where those meetings took place.

Local health authorities in states like North Dakota, as well as in countries such as Canada and the United Kingdom, say they’ve pleaded with the companies to give them more control over the kinds of information their apps can collect. Without the companies’ help, some worry their contact tracing systems will remain dangerously strained.

But Apple and Google have refused, arguing that letting the apps collect location data or loosening other smartphone rules would undermine people’s privacy. The companies are also concerned that easing the restrictions around apps’ Bluetooth use would drain phone battery life, which could irritate customers. That unbending stance has led some health authorities to abandon hopes of building a fully functioning contact-tracing app.

The struggle for effective digital contact tracing is reshaping the debate over the trade-offs between privacy and public health where lives are immediately at stake. Public officials say the need to understand how the virus is spreading is urgent, informing decisions about whether communities can reopen and detecting future outbreaks.

But the tech giants’ resistance to letting public health officials access people’s data has a long precedent of keeping personal information out of the hands of governments. Apple and Google said they contacted hundreds of public health officials for input on the software before it was announced.