On Tuesday, data on the delta variant prompted the Centers for Disease Control and Prevention to change its mask guidelines: The agency now says fully vaccinated people in areas with substantial or high coronavirus transmission should wear masks in public indoor settings.

Evidence suggests the delta variant makes many more copies of the coronavirus in people it infects.

But how can people with breakthrough cases tell if they have delta?

“ASU is routinely monitoring its positive cases, but it takes about a week to two weeks to get those answers back, and they are not reportable to the individual,” said Joshua LaBaer, executive director of ASU's Biodesign Institute. 

LaBaer says that’s because no CLIA-approved test exists that would provide such answers. CLIA, an acronym for the Clinical Laboratory Improvement Amendments of 1988, governs work with human blood, tissue or other samples for diagnosis, prevention or treatment purposes.

But LaBaer also pointed out that the variant accounts for 8 in 10 cases in the state. He added that he expects that proportion to rise. 

"So there's a pretty good bet that, if you have a breakthrough case, you have delta in Arizona right now.”