Large-scale testing, not individual testing, tells when delta variant causes COVID-19

Public health experts say the delta variant of the SARS-CoV-2 coronavirus appears to be twice as contagious as the original coronavirus, and has become the dominant strain in the United States.

So, we must have a test that diagnoses this new mutation, right?

With a rhetorical question, a meme that shows a pensive Albert Einstein doubts the existence of the variant by claiming there is no test for it, saying:  

"SINCE THERE IS NO ‘DELTA VARIANT’ TEST EXACTLY HOW ARE PEOPLE BEING DIAGNOSED WITH DELTA VARIANT."

The post was flagged as part of Facebook’s efforts to combat false news and misinformation on its News Feed. (Read more about our partnership with Facebook.)

No one is being diagnosed with the delta variant, or any other variant. Routine tests that individuals receive to determine whether they have COVID-19 do not reveal whether the disease was caused by the delta variant. 

But through what is known as genomic sequencing, public health officials examine samples of cases to estimate what percentage were caused by delta.

Genomic sequencing from a positive test sample, said Stephen Morse, professor of epidemiology at Columbia University Medical Center, "would tell you unequivocally what variant infected that person."

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A variant of the coronavirus that causes COVID-19 is one that has mutated in a way that bolsters its spread or severity compared with the original strain that emerged in Wuhan, China. Public health officials have noted four "variants of concern" circulating in the United States, including delta, formally called B.1.617.2. Discovered in India in December 2020 and in the U.S. in March 2021, it is the most transmissible of the four variants. While it is not yet known if the delta produces more serious illness, it threatens to accelerate the spread of the pandemic.

If individual testing doesn’t reveal delta, how do we know it is in play?

The federal Centers for Disease Control and Prevention explains how it tracks variants by analyzing some 750 samples per week from state health departments and other public health agencies and making estimates:

"The SARS-CoV-2 genome encodes instructions organized into sections, called genes, to build the virus. Scientists use a process called genomic sequencing to decode the genes and learn more about the virus. Genomic sequencing allows scientists to identify SARS-CoV-2 and monitor how it changes over time into new variants, understand how these changes affect the characteristics of the virus, and use this information to better understand how it might impact health."

In the U.S., delta is the cause of more than 80% of new COVID-19 cases, according to the CDC.

Individuals are not being diagnosed with the delta variant.

Routine individual tests don’t reveal whether COVID-19 was caused by the delta variant. Scientists use genomic sequencing to determine what percentage of cases were caused by the variant. 

This post contains an element of truth, but ignores critical facts that would give a different impression. 

We rate it Mostly False.