Politicians and scientists in Britain are concerned that people are deleting the official Covid-19 mobile phone app, or at least switching off its tracing function, to avoid having to self-isolate.
Just fewer than 620,000 people in England and Wales were "pinged" by the National Health Service Covid-19 app and told to isolate in the past week - a record, and up from around 530,000 the week before, official figures show.
Yet the recent rate of growth in app alerts has been slower than the increase in Covid-19 infections. That has stirred warnings that amid the growing furore about a "pingdemic" and its impact on key industries, more people are simply disabling a key part of the app that the government and health experts say is critical to halting the spread of the disease.
The fear is that public trust in the test, trace and isolate programme as a whole is eroding, just as virtually all pandemic rules were lifted in England this month.
"It isn't rocket science: If you're asking people to do something that's difficult for them, guess what - they're not going to do it," said Professor Henry Potts at University College London, who specialises in health data.
"Isolating is difficult, it's inconvenient - for some people it's very difficult." Prof Potts said surveys show an increase in the number of app deletions in the last few months, and that suggestions ministers were considering tweaking the app to make it less sensitive had been "unhelpful".