Scientists decode likely order of COVID-19 symptoms

Scientists have found the likely order in which COVID-19 symptoms first appear, an advance that may help clinicians rule out other diseases, and help patients seek care promptly or decide sooner to self-isolate. According to the study, published in the journal Frontiers in Public Health, the likely order of symptoms in patients with COVID-19 is fever, followed by cough, muscle pain, and then nausea, and/or vomiting, and diarrhea.

"This order is especially important to know when we have overlapping cycles of illnesses like the flu that coincide with infections of COVID-19," explained study co-author Peter Kuhn, a professor of medicine and biomedical engineering at the University of Southern California (USC) in the US.

With this new information, Kuhn said doctors can determine what steps to take to care for patients, and prevent their condition from worsening. The researchers believe identifying patients earlier may reduce hospitalisation time since there are better approaches to treatments now for COVID-19 than during the beginning of the pandemic.

In the current study, the scientists predicted the order of symptoms from data on the rates of symptom incidence of more than 55,000 confirmed coronavirus cases in China, all of which were collected from February 16 to 24 by the World Health Organization (WHO).

They also studied a dataset of nearly 1,100 cases collected from December 11, 2019 through January 29, 2020, by the China Medical Treatment Expert Group via the National Health Commission of China. To compare the order of COVID-19 symptoms to that of influenza, the scientists examined flu data from 2,470 cases in North America, Europe and the Southern Hemisphere, which were reported to health authorities from 1994 to 1998.

"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," said Joseph Larsen, study lead author from USC.

While fever and cough are frequently associated with a variety of respiratory illnesses, including Middle East Respiratory Syndrome (MERS) and Severe Acute Respiratory Syndrome (SARS) which caused the 2002-03 pandemic, they said the timing and symptoms in the upper and lower gastrointestinal tract set COVID-19 apart.

"The first two symptoms of COVID-19, SARS, and MERS are fever and cough. However, the upper GI tract (nausea/vomiting) seems to be affected before the lower GI tract (diarrhea) in COVID-19, which is the opposite from MERS and SARS," the scientists wrote in the study. According to the research, a very small fraction of patients experienced diarrhea as an initial symptom.

"This report suggests that diarrhea as an early symptom indicates a more aggressive disease, because each patient in this dataset that initially experienced diarrhea had pneumonia or respiratory failure eventually," the scientists wrote.

"The highest reported symptom is fever, followed by cough or dyspnea, and then finally, a small percent of patients reported diarrhea. This order confirms the most likely paths that we have determined," they noted.