How many days are you contagious with the delta variant?

After weeks of rapidly increases case numbers, the US is finally beginning to see a decline in new cases after experiencing a brutal fifth wave.

After hitting a peak of over 169,000 cases on 18 August, on Monday 22 August, just under 44,000 cases were confirmed.

How does delta vary from previous strains?

The Centers for Disease Control and Prevention (CDC) released new information describing what is known about the Delta variant. This includes the fact that the strain is twice as contagious as those previously circulating in the US and some new data that shows that the “Delta variant might cause more severe illness” in those unvaccinated.

Delta leads to a positive test more quickly when compared to other strains

With previous strains of the virus, most patients tested positive after around six days of their exposure. However, scientists from the Massachusetts Institute of Technology found that individuals infected with Delta are “testing positive two days earlier, on average, they were also way more infectious by the time their infections were detectable." 

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Are those infected with Delta contagious for longer periods?

In some cases, yes.

The most important variable in answering this question is vaccination status. While the CDC has said that fully vaccinated people can spread the virus, new science shows they may be infectious for a short period of time.

When a vaccinated person is infected, known as a breakthrough case in the scientific community, they generally produce less virus as their immune system can respond to the threat more quickly.

However, with Delta, breakthrough cases are being seen more frequently because “ the Delta variant seems to produce the same high amount of virus in both unvaccinated and fully vaccinated people.” 



Anyone vaccinated or not who tests positive should wear a mask in public for fourteen days or until they test negative for the virus.

However, for those who have received their shots, the amount of virus produced slows much more quickly, leading scientists to believe that “fully vaccinated people are likely infectious for less time than unvaccinated people.”

What are breakthrough cases, and how common are they with the Delta variant?

One key fact about breakthrough cases that the CDC wants to make clear to the public is that they are expected. Epidemiologists and public health experts have long thought that there would be a strain that could increase the frequency that vaccinated people become infected.

Sadly, the covid-19 pandemic has led to 622,833 deaths as of 22 August; 1,829 were traced to those who had received a covid-19 vaccine.

While concerning and tragic, these fatal cases of covid-19 represent a small minority of deaths. The CDC has stated that while not 100% effective in preventing infection, “the vaccine still provides them strong protection against serious illness and death.”