Covid Update: “Test to Treat” and “Deltacron”

“Test to Treat” – President Biden announced a “test to treat” program to combat COVID-19 in his State of the Union address on March 1st. The concept is that any vulnerable individual with COVID symptoms could go to a local pharmacy, take a rapid COVID test, and, if positive, be given one of two licensed antiviral pills. Rapid tests are now readily available, but the two antiviral drugs are in short supply and must be prescribed by a licensed health care specialist. 


The two antiviral pills authorized by the FDA are Paxlovid from Pfizer and Molnupiravir from Merck. The Pfizer pill reduces hospitalizations by 90% if started soon after symptoms appear, but it does interact with other drugs so that a detailed medical history is required. Production is being ramped up, but it is still difficult to access as of this writing. Molnupiravir is less effective and has potential reproductive side effects, concerns that make it seem less likely to be widely adopted. CVS Minute Clinics are one site that has agreed to participate in the test to treat program. Fortunately, the waning Omicron epidemic mean that a wait for this program to be fully implemented should be acceptable.


“Deltacron” – Several recent news reports have created concern about a novel COVID-19 virus that is half Delta and half Omicron, which has been dubbed “Deltacron”. It sounds scary, but it likely isn’t. A recent preprint from Helix Laboratories in San Mateo, CA described samples from two subjects that had gene segments from both Delta and Omicron variants, although both had the critical spike protein (the target of vaccines) derived from the Omicron genes. This type of recombination requires that the infected individual not only harbored both the Delta and the Omicron variant, but they also had to copy their genes in the same infected cell. The Helix study analyzed COVID virus sequences from 29,719 patient samples, and they found 20 instances of dual infections and only 2 samples with the recombinant Delta:Omicron (“Deltacron”) genetic sequence. Bottom line: these recombinant viruses are exceedingly rare and unlikely to generate a new wave of infections. Ongoing genetic sequencing studies are monitoring for new “viruses of concern,” but “Deltacron” is not in that category. 


As a footnote, it is worth noting that the initial report of a “Deltacron” variant was likely a result of laboratory contamination (Nature, 21 January 2022), but the name stuck when true recombinant viruses were identified. A standard nomenclature for recombinant COVID viruses is being developed, and it is likely that “Deltacron” will be called “XD”, which doesn’t sound nearly as dangerous or newsworthy.