COVID-19 symptoms appear in a specific order, study finds

One reason to suspect you have COVID-19 may be the order in which the symptoms appear.

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  • USC researchers identify a distinct order in which COVID-19 symptoms present themselves.
  • SARS-CoV-2 affects the digestive tract in a way that distinguishes it from other similar infections.
  • If you experience these symptoms in this order, call your doctor.

One of the scary things about COVID-19 is that the early symptoms it presents are also common indicators of a flu or infection: fever, cough, and so on. When a person experiences any of these symptoms these days, it's reasonable to wonder if they have COVID-19.

Now researchers from the Kuhn Lab as University of Southern California have discovered something that may be useful for anyone questioning whether they've been infected with COVID-19. According to their investigation, it's likely that coronavirus symptoms present in a particular order. This is unusual — other illness that produces these symptoms don't follow any known sequence — and if a person gets these symptoms in this particular order, they should self-isolate and get tested.

The study is published in Frontiers in Public Health.

The symptoms in order

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The USC team says that coronavirus' symptoms present in this order:

  1. fever
  2. cough and muscle pain
  3. nausea and/or vomiting
  4. diarrhea

What really sets apart COVID-19 from other diseases is the timing of the nausea/vomiting and diarrhea. While the respiratory symptoms are similar to those associated with Middle East respiratory syndrome (MERS) and severe acute respiratory syndrome (SARS), the gastrointestinal sequence of COVID-19 is distinctive. COVID-19 attacks the upper GI tract first, causing nausea/vomiting before moving down to the lower GI tract, producing diarrhea. This is the opposite of the way in which these symptoms appear with MERS and SARS.

"This order is especially important to know when we have overlapping cycles of illnesses like the flu that coincide with infections of COVID-19, says study co-author Peter Kuhn. "Doctors can determine what steps to take to care for the patient, and they may prevent the patient's condition from worsening."

The study calls for further investigation into the presenting symptoms of COVID-19, since unanswered questions remain. Might the order of symptoms vary with outlier strains of SARS-CoV-2? Do other risk factors such as obesity, or environmental factors such as temperature affect their order?

Clue in the data

The core data set used by the USC team were case histories of 55,000 people who contracted COVID-19 in China. The data was collected by the World Health Organization from February 16-24, 2020. Their analysis was supplemented by data from almost 1,100 additional cases documented by the China Medical Treatment Expert Group via the National Health Commission of China — these came from December 11, 2019 to January 29, 2020.

To assess the similarity of COVID-19's symptom ordering to the flu, the researchers looked at the data from 2,470 North American, European, and Southern Hemisphere flu cases from 1994 to 1998.

Early diagnosis

"The importance of knowing first symptoms is rooted in the need to stop the spread of COVID-19, a disease that is two to three times more transmissible than influenza and results in outbreaks of clusters.' — Larsen, et al

Lead study author Joseph Larsen says that in addition to slowing transmission, an understanding of COVID-19's progression could also facilitate more effective treatment.

"The order of the symptoms matter. Knowing that each illness progresses differently means that doctors can identify sooner whether someone likely has COVID-19, or another illness, which can help them make better treatment decisions," says Larsen, who adds, "Given that there are now better approaches to treatments for COVID-19, identifying patients earlier could reduce hospitalization time."