By Dr. James Katz, MD, MPH

The Delta variant of COVID-19 is the fourth major mutation of the pandemic. It has modified spike proteins which attach more efficiently to human cells than the original COVID-19. Its genetic programming is more potent — infected cells produce a thousand times more virus particles than its predecessor. A person with Delta is infectious at days four to ten, or 50% longer than COVID-19. Unvaccinated people of all ages, when hospitalized with Delta, are twice as likely to need mechanical ventilation. Vaccinated people can get a flu type illness (with no loss of smell). The Delta variant “is faster, it is fitter, and it will pick off the more vulnerable more efficiently than previous variants,” warned Dr. Mike Ryan, the executive director of the World Health Organization’s Health Emergencies Program.

R naught is a measure of infectivity. The original COVID-19 was rated 2.5 in China.  In the US, it was 3.3 in Queens, New York at the peak.  Data analyst Tomas Pueyo, compared the R naught (R0) values — a mathematical measure of contagion — of the Delta and original variants. His comparative model, which placed the R0 of the original strain at 2.7 and that of Delta at 6. R naught is an exponential scale, so Delta is potentially 1,000 times more infectious than the original COVID-19 epidemic. (Forbes July13, 2021)

Those masks sitting in your closet need to be worn again. Your unvaccinated risk of getting Delta is formidable, and it is more dangerous. Share on X

In simple terms, the person in front of you in line at the grocery store may be exhaling highly concentrated clouds of more dangerous virus particles. In settings where 40 minutes exposure could transmit COVID-19, you can get Delta in five minutes. In a computer model, where COVID-19 infected 42,000 people in a month, Delta infected 520,000 people. (Modeling based on CDC data)

I’m a doctor and I am vaccinated. I am back to wearing a mask in enclosed or crowded spaces and washing my hands. I am still going to well-ventilated restaurants, but not bars. Meeting people outdoors is fine, but take care indoors.

Those masks sitting in your closet need to be worn again in closed spaces with people you don’t know. Your risk of getting Delta (unvaccinated) is formidable, and it is more dangerous. Your risk (vaccinated) of getting Delta, causing 5-10 day flu (burning sore throat and prominent headache) is real; and if vaccinated, asymptomatic transfer to friends, family, or coworkers is predictable.

A mask will still protect you from others, and protect others from you.

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