Main Delta COVID Variant Symptoms May Be Different From Original Virus

The main symptoms produced by the Delta COVID-19 variant first identified in India may be different to those experienced by people who were infected with the original lineage of the virus, research has suggested.

The Delta variant, also known as B.1.617.2, and its sub-lineages have now been detected in more than 70 countries. In some places, it is spreading fast. This includes the U.K., where it now accounts for over 90 percent of new cases.

The findings come from the ZOE COVID Symptom Study—an initiative created by researchers at Massachusetts General Hospital, the Harvard T.H. Chan School of Public Health, King's College London and Stanford University School of Medicine, in collaboration with health science company ZOE, to study the symptoms of the disease and track its spread using an app.

Tim Spector, who runs the ZOE study, said data collected by the app in the U.K. suggests that the main symptoms of the Delta variant may be slightly different to the classic symptoms.

According to the Centers for Disease Control and Prevention (CDC), the most common symptoms of COVID-19 are fever, dry cough and tiredness.

But according to Spector, the most commonly reported symptoms linked to COVID-19 infections over the past few weeks in the U.K., where the Delta variant is dominating, appear to be headache, sore throat and runny nose.

"What's really important to realize is that since the start of May, we've been looking at the top symptoms in all the app users, and they're not the same as they were. So the number one symptom is headache... followed by sore throat, runny nose, and fever," Spector said in a video update produced by ZOE.

"Number five is cough, it's rarer. And we don't even see loss of smell coming into the top 10 anymore. This variant seems to be working slightly differently," he said.

Spector also said that catching the Delta variant seems to be more like a "bad cold" in younger people.

"People don't realize that and [it] hasn't come across in the government information. This means that people might think they've just got some sort of seasonal cold, and they still go out to parties, and they might spread around to six other people," he said in the video.

Spector said the Delta variant appears to be around twice as transmissible as the original variant, meaning that one person will, on average, infect around six others in normal non-lockdown conditions.

It is "really very infectious," he said. "This is a very sticky virus. And it's explaining in a way why it's done so much damage in a short time, despite the lack of individuals to actually attack."

The Delta variant has also been identified in the U.S. On Sunday, the former commissioner of the Food and Drug Administration, Scott Gottlieb, told CBS' Face the Nation that the variant is likely to become the main source of new infections in the country.

"Right now, in the United States, it's about 10 percent of infections," he said. "It's doubling every two weeks. "That doesn't mean that we're going to see a sharp uptick in infections, but it does mean that this is going to take over. And I think the risk is really to the fall that this could spike a new epidemic heading into the fall."

But Gottlieb said that the vaccines approved for use in the U.S. and abroad appear to still be highly effective against the variant.

"We have the tools to control this and defeat it. We just need to use those tools," he said.

Spector said that in people who are fully vaccinated, there appears to be some reduction in protection given by the vaccines but it only appears to be "very minor."

"Your risk is still at least five- to tenfold less if you've been double vaccinated, and we know from our data from the ZOE app, that if you get it, you're going to get a much milder shorter duration version, make it highly unlikely you're going to go to hospital. So that is a really good reason to get that double shot."

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Coronavirus particles
Artist's illustration of coronavirus particles. The main symptoms of the Delta COVID-19 variant may be slightly different to the original virus, research has suggested. iStock