Another CDC data flub distorts delta variant contagiousness. The Centers for Disease Control and Prevention (CDC) claimed the delta variant of COVID-19 is "as transmissible as" chickenpox. It's not true.
Chickenpox, caused by the varicella-zoster virus, is one of the most contagious diseases we know of. "If one person has it, up to 90% of the people close to that person who are not immune will also become infected," states the CDC website.
One person infected with chickenpox will infect an average of 10 people when everyone in a population is vulnerable to catching it. (This transmissibility number—referred to as R0—goes down when people have immunity to the disease.)
"The initial COVID-19 strain had an R0 between two and three," computational biologist Karthik Gangavarapu told NPR. The delta variant has an R0 between six and seven. For chickenpox, the R0 is nine or 10.
How did the CDC conclude that these were equivalent?
For one, the leaked document underestimated the R0 for chickenpox and overestimated the R0 for the delta variant. "The R0 values for delta were preliminary and calculated from data taken from a rather small sample size," a federal official told NPR. The value for the chickenpox (and other R0s in the slideshow) came from a graphic from The New York Times, which wasn't completely accurate.
Apparently, the federal agency charged with disseminating COVID-19 data and setting public health policy is taking its cues from a newspaper infographic. Oh my.
Using more accurate data, the delta variant proves more transmissible than O.G. COVID but less transmissible than the virus behind the chickenpox.
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