COVID-19 has always been tricky to identify because the symptoms easily overlap with the common cold, flu, and even allergies. Even more confusing? Some people experience no symptoms at all.
To better understand how COVID-19 manifests and progresses, a team of researchers at the University of Southern California attempted to figure out the most common order in which symptoms appear.
Their study, which was recently published in the journal Frontiers in Public Health, analyzed the rates of COVID-19 symptom incidences. They used data collected from the World Health Organization of more than 55,000 novel coronavirus cases in China, as well as a dataset of nearly 1,100 cases collected by the National Health Commission of China.
Based on their findings, the researchers determined that this is the most likely order that someone will experience COVID-19 symptoms:
- Nausea and/or vomiting
When they expanded their analysis to include additional symptoms, the order still looked similar:
- Sore throat, muscle pain, or headache
- Nausea and/or vomiting
The researchers also compared the likely progression of COVID-19 symptoms against the flu and found that the flu was more likely to start with a cough instead of a fever. People with the flu were also more likely to have body aches, headache, and a sore throat before developing a fever, they discovered.
In turn, these results “support the notion” that fever should be used to screen people for COVID-19 before they’re allowed into buildings. “Additionally, our findings suggest that good clinical practice should involve recording the order of symptom occurrence in COVID-19 and other diseases,” the authors wrote.
But infectious disease experts say the order of your COVID-19 symptoms doesn’t paint the whole picture.
William Schaffner, M.D., an infectious disease specialist and professor at the Vanderbilt University School of Medicine says the results of this study are “very interesting,” but emphasizes that “it’s not going to be universal. We know, for starters, that a number of people don’t have a fever.”
What’s more, there’s the issue of recall bias, which is when patients have a hard time remembering exactly when something happened. “It’s common with these kind of things,” says Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security. “You won’t be able to tell people, ‘You have COVID-19 because you had symptoms in this order versus a different order.’”
Instead, experts say that it’s important to pay attention to any unusual symptoms associated with COVID-19, regardless of when they appear. This includes chills, shortness of breath, fatigue, loss of taste or smell, runny nose, or congestion in addition to the list above.
“If someone presents with cough first and fever afterwards, I wouldn’t assume it’s not COVID,” says Thomas Russo, M.D., professor and chief of infectious disease at the University at Buffalo. “It’s an interesting guide, but you should never let symptoms alone drive whether or not you should do a test.” He adds that doctors should “have a low threshold” with any respiratory symptoms right now, no matter their order.
That said, the data can still be helpful in further understanding COVID-19, as it’s caused by a newly discovered coronavirus that still requires a vast amount of research. “This is a good starting point for people,” says Rajeev Fernando, M.D., an infectious disease expert in Southampton, New York. He’s noticed his patients tend to follow a similar trajectory to the one in the study, with additional symptoms like loss of smell and taste following the fever and cough.
Bottom line: Ask about getting tested if you experience any COVID-19 symptoms, but keeping track of when your symptoms started to appear and how they progressed may be helpful information for your doctor.