- Classical symptoms of COVID-19 follow a distinct sequence, a new study has found.
- Patients usually start with a fever, followed by a cough. Some may later develop gastrointestinal problems.
- Diarrhea may be an early sign of a more serious case, according to the study.
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The official list of symptoms of COVID-19 continues to grow. The Centers for Disease Control and Prevention now associates 11 symptoms with the disease, although some patients have reported conditions that do not appear on that list, such as hair loss, hiccups, and purple, swollen toes.
“I have never seen an infection with this wide range of manifestations,” said Drs. Anthony Fauci, the director of the National Institute of Allergy and Infectious Diseases, Facebook founder Mark Zuckerberg last month.
This can make cases of coronavirus difficult to characterize. But a recent study from the University of Southern California identified a distinct sequence of symptoms among nearly 56,000 patients with COVID-19.
The researchers found that most symptomatic patients start with a fever, followed by a cough. Afterwards, they may experience a headache, headache, or muscle aches and pains, followed by nausea or vomiting, then, finally, diarrhea.
For the most part, the researchers found, patients with milder cases thought the same sequence of symptoms as those with severe cases. But diarrhea could be a sign of a more severe infection, they found.
“This report suggests that diarrhea as an early symptom indicates a more aggressive disease, because every patient in this dataset who had originally experienced diarrhea had pneumonia or respiratory failure,” the researchers wrote.
The CDC has also found that some COVID-19 patients may have diarrhea before developing fever.
However, diarrhea was relatively uncommon among the COVID-19 patients examined in the new study: under 4% of patients had it, compared with 88% who had a fever and 68% with a cough. Other, smaller studies have found diarrhea to be more common among patients with hospital COVID-19: between 10% and 34%.
Defining a ‘classic’ case of COVID-19
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Defining a typical progression of COVID-19 symptoms can help officials determine which public health measures are particularly useful for preventing the spread of the virus.
“The order of the symptoms is important,” Joseph Larsen, lead author of the new study, said in a statement. “Knowing that each disease progresses differently means that doctors can identify sooner if someone is likely to have COVID-19, or another disease that may help them make better treatment decisions.”
For example, since COVID-19 patients are now understood to be most infectious at the onset of their illness, a fever may be a sign that a person is contagious (although humans may also be contagious before their symptoms begin). This means that temperature controls can be a useful tool.
“Our results support the idea that fever should be used to screen for entry into facilities as regions begin to recover,” the researchers wrote.
Through the new research, medical professionals can also better distinguish between COVID-19, SARS, and MERS (which are all coronaviruses). With the last two, patients also started having a fever, followed by a cough, according to the study. But unlike COVID-19 patients, they tended to develop diarrhea before nausea or vomiting.
COVID-19 also starts differently than seasonal effects: The researchers found that people with the flu develop a cough for a fever.
There is more to learn about coronavirus symptoms
Of course, there are limitations to these findings. The researchers’ data comes from Chinese cases reported by the World Health Organization in February. But cases confirmed that early in the pandemic tended to be more severe and included hospitalization so the data could be outlined. The authors stress the need to replicate their results for patients in the US and elsewhere.
The CDC also estimates that approximately 40% of coronavirus patients are asymptomatic – meaning that a significant proportion of coronavirus cases do not follow the pattern described in the study.
For that reason, there is still a lot to learn about what a “typical” case looks like.
“One of the things we have learned about the virus is not to underestimate it and not to rule out that something is coronavirus just because it does not fit our model of what coronavirus is,” Drs. Nate Favini, the medical lead at Forward, a primary care practice that collects data on coronavirus patients around the country, told Business Insider. “Given the asymptomatic spread of the virus, it’s almost like you have to act like someone could have coronavirus until proven otherwise.”
