Is there an order in which Covid-19 symptoms first appear? Study says it may be fever, cough and muscle pain
Knowing which symptoms show first can help doctors identify Covid-19 patients sooner and make better treatment decisions, say researchers
People with coronavirus have reported a wide range of symptoms – ranging from mild to severe illness. According to health experts, symptoms may appear 2-14 days after exposure to the virus. But is there a likely order in which coronavirus symptoms first appear? Scientists from the University of Southern California (USC) say that they have identified this order and it is fever, cough and muscle pain, then nausea and/or vomiting, and then diarrhea.
According to the researchers, knowing the order of Covid-19 symptoms may help patients seek care promptly or decide promptly to self-isolate. It also could help doctors rule out other illnesses or plan how to treat patients, and perhaps intervene earlier in the disease, they explain. “This order is especially important to know when we have overlapping cycles of illnesses like the flu that coincide with infections of Covid-19. Doctors can determine what steps to take to care for the patient, and they may prevent the patient’s condition from worsening,” says Peter Kuhn professor of medicine, biomedical engineering, and aerospace and mechanical engineering at the USC Dornsife College of Letters, Arts and Sciences.
Why this study?
The authors explain that identifying Covid-19 early could reduce the number and size of clusters, but early symptoms are not well-defined. They say that they are not proposing initial symptom as a diagnostic test, but instead, as a possible sign to get tested. Covid-19 outbreaks in clusters and these unusual clusters of the disease are characteristic of a pandemic disease that must be addressed immediately with aggressive testing to curb transmission, the team cautions.
“The importance of knowing the 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. There is a heightened risk in Covid-19 being passed on, so faster testing and social distancing are important, especially when social distancing and quarantine measures are relaxed,” says the study published in Frontiers in Public Health.
The Center for Disease Control and Prevention (CDC) and the World Health Organization (WHO) currently advise people to call their doctor if they believe they have been exposed to Covid-19 or exhibit fever and cough. However, fever and cough are associated with other respiratory diseases such as influenza, say experts. Similarly to Covid-19, the Middle East Respiratory Syndrome (MERS) and the Severe Acute Respiratory Syndrome (SARS) are respiratory illnesses contracted from coronaviruses, says the study. The symptoms of these diseases also overlap with Covid-19, and therefore, the capacity to discern differences in these common symptoms, such as order of occurrence and likely first symptoms, would aid in early recognition, the team emphasizes.
“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,” writes Joseph Larsen, the study’s lead author and a USC Dornsife professor. “Given that there are now better approaches to treatments for COVID-19, identifying patients earlier could reduce hospitalization time,” adds Larsen.
What did the scientists find?
Patient data from the study was collected from various reports in the literature on the frequencies of symptoms in Covid-19, influenza, MERS and SARS. The research team analyzed the rates of symptom incidence of more than 55,924 confirmed coronavirus cases in China, all of which were collected by the WHO from February 16 to 24. They also studied a dataset of 1,099 cases collected from December 11 to January 29 by the China Medical Treatment Expert Group via the National Health Commission of China. To compare the order of Covid-19 symptoms to influenza, the researchers examined data from 2,470 cases in North America, Europe and the Southern Hemisphere that were reported to health authorities from 1994 to 1998. The authors also looked at datasets representing symptom frequency in MERS and SARS patients.
The analysis reveals that influenza typically begins with a cough, whereas Covid-19 like other coronavirus-related diseases such as SARS and MERS starts with a fever. However, Covid-19 differs from SARS and MERS in the order of gastrointestinal symptoms. The timing and symptoms in the upper and lower gastrointestinal tract set Covid-19 apart. In Covid-19 patients, the upper gastrointestinal (GI) tract (that is, nausea/vomiting) seems to be affected before the lower GI tract (that is, diarrhea). This is the opposite of MERS and SARS, where the lower gastrointestinal tract is usually impacted first, leading to diarrhea before nausea and vomiting.
The authors say that the findings support the idea that symptoms occur in a predictable order, but future work is needed to confirm the results. They add that the results support the notion that fever should be used to screen for entry into facilities as regions begin to reopen.
“In this study, we found evidence that supports the notion that there is a most common order of discernible symptoms in Covid-19 that is also different from other prominent respiratory diseases. The most likely initial symptom is fever in the three diseases studied that are caused by coronaviruses (Covid-19, SARS, and MERS) and cough in influenza,” write authors. They add, “The most likely order of the four easily discernible symptoms is identical in MERS and SARS, but the most likely path of Covid-19 has one key difference. The first two symptoms of Covid-19, SARS, and MERS are fever and cough. However, the upper GI tract seems to be affected before the lower GI tract in Covid-19, which is the opposite from MERS and SARS.”
According to the authors, the findings suggest that good clinical practice should involve recording the order of symptom occurrence in Covid-19 and other diseases. “If such a systemic clinical practice had been standard since ancient diseases, perhaps the transition from local outbreak to pandemic could have been avoided,” they suggest.