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Delta Variant Causes Different Symptoms To "Classic" COVID, Top Scientists Says


Tom Hale

Senior Journalist

clockJun 14 2021, 15:40 UTC

CCL-81 cells heavily infected with SARS-CoV-2 virus particles. The small spherical structures in the center of the image are SARS-CoV-2 virus particles. The string-like protrusions extending from the cells are cell projections or pseudopodium. Image Credit: NIAID (CC BY 2.0)

The Delta variant, previously known as the Indian variant, appears to cause different symptoms to those seen in “classic” COVID-19, according to the leading scientists behind the Zoe COVID Symptom study.

The three main symptoms seen in a typical COVID-19 infection are a fever, a cough, and a loss of taste or smell. However, the most commonly reported symptoms of people infected since May 2021 appear to be a headache, a sore throat, and a runny nose. Loss of taste or smell — once considered an easily identifiable symptom of COVID-19 — isn't even in the top 10 most commonly reported symptoms anymore. 


Professor Tim Spector, a genetic epidemiologist at King's College London who runs the Zoe COVID Symptom study, says the change in symptoms being reported is most likely due to the rising prominence of the Delta variant, which recently became the UK’s most dominant strain.

"Since the start of May, we have been looking at the top symptoms in the app users, and they are not the same as they were," Professor Spector explained in a video on June 09 (below).

"This variant seems to be working slightly differently."


Professor Spector explained that catching the Delta variant can feel "more like a bad cold" for healthy younger people. Nevertheless, others still remain at high risk of falling seriously ill with the infection. 

"People might think they've just got some sort of seasonal cold and they still go out to parties and they might spread it around to six other people," he continued. 

"We think this is fuelling a lot of the problem." 


The Delta variant is said to be hyper-infectious and likely more severe than its relatives. The original variant had an R0 of around three, meaning an infected person would infect three others on average in normal conditions, while the Delta variant has an R0 of six, meaning it’s effectively twice as transmissible as the original variant. Analysis of hospital admission rates has suggested people infected by the Delta variant are twice as likely to be hospitalized than those with the Alpha variant, first identified in the UK.

Due to its aggressive nature, the Delta variant is thought to be the driving force behind many of the severe recent outbreaks seen across the world, especially in India where it was first identified. It currently accounts for around six percent of US infections. 

Other countries have also noticed that the Delta variant is a very different beast from the original strain. As reported in the New York Times this weekend, the Delta variant has recently hit southeastern China. Doctors treating COVID-19 patients in China have noticed that the virus is notably more dangerous than it was when it first emerged in the country in late 2019. They too have realized the variant is causing different symptoms.


Meanwhile, in India, doctors have reported patients suffering from hearing loss, severe stomach upsets, and blood clots leading to gangrene, symptoms not typically seen in most COVID-19 patients. 

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