Study tracks growing list of COVID-19 symptoms in real time

When the novel coronavirus first emerged in China, the world was warned to watch out for two main symptoms: fever or a persistent cough.

A lot has changed since then.

The US Centers for Disease Control and Prevention now lists seven symptoms, and the World Health Organization includes even more, with a breakdown of which ones appears to be more or less common. On Monday, the United Kingdom also added loss of smell and taste to the growing list of symptoms.

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Researchers are learning that symptoms of the coronavirus can vary depending on myriad factors, such as age and health status. And they’re seeing other conditions they hadn’t connected to the disease earlier on, including in children.

Although cases of the coronavirus in children are few and far between, doctors have recently observed a syndrome they say is probably linked to COVID-19. Some children have experienced a rare condition involving an overreaction of the immune system and requiring intensive care.

“I call on all clinicians worldwide to work with your national authorities and WHO to be on the alert and better understand this syndrome in children.”

“I call on all clinicians worldwide to work with your national authorities and WHO to be on the alert and better understand this syndrome in children,” said WHO director-general Dr. Tedros Adhanom Ghebreyesus.

The COVID Symptom Study is pulling together this growing list of the coronavirus symptoms in real-time. Since its app launched in March, it has crowdsourced symptoms from more than 3.5 million people in the UK, US and Sweden.

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“There are a few other ones we’ve added recently like acute muscle pains, hives of the face and skin rashes,” said Dr. Timothy Spector, a professor of genetic epidemiology and a doctor at King’s College in London and co-director of the study. “We’ve also got chest pain, abdominal pain, shortness of breath, hoarse voice, confusion, diarrhea. Important ones are fatigue, anorexia and loss of smell and taste.”

That last one — loss of smell and taste — caught the group’s attention. Spector and others with the project had a study in the journal Nature last week showing that the loss of smell and taste was higher in those with a positive test result — around 65% reported it — compared to those with a negative test result — about 21.7%.

But it may be confusing for people to know whether a loss of smell or taste has to do with something like spring allergies as opposed to COVID-19. One indicator is that a person has never experienced such symptoms before.

The reason symptoms vary so wildly may depend on how people’s immune systems respond to the virus, but scientists are still learning. Through the study, researchers are able to zoom out and track trends at a population level.

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Spector is also interested in how genetics comes into play as well as people’s guts, or microbiomes.

“In my career, I’ve never seen any disease that has such a variable effect in people and can affect nearly every part of the body as well.”

“In my career, I’ve never seen any disease that has such a variable effect in people and can affect nearly every part of the body as well.”

Clusters of symptoms may be an indicator of the disease and its spread, according to Dr. Andrew Chan, an epidemiologist at Harvard’s T.H. Chan School of Public Health and lead researcher of the project. One example might be groups of people reporting a combination of abdominal pain, acute loss of smell and a stuffy nose.

The hope is that such knowledge and data could better identify outbreaks.

“Our understanding of the symptoms has changed as a result of the data we’re collecting,” he said. “That [data] has been returned to public health authorities as a way to better track where we’re actually seeing incidence.”

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The need to get a better, real-time clinical picture of COVID-19 is critical, said Eleanor Murray, an assistant professor of epidemiology at Boston University who wasn’t involved in the study.

Tracking self-reported symptoms in this way can help researchers identify symptoms that might not be on their radar, she said. But Murray cautioned that the study has limits: It only captures those who use the app.

“Who downloads that app, who uses that app, who has access to a smartphone?” she said, adding that the app may miss young children and the elderly.

The fact that more people may be primed to report symptoms that they’re more aware of now might also throw off the data somewhat, she said.