An early alteration in the virus that causes COVID-19 appears to have shifted the order in which symptoms developed in individuals. COVID-19 individuals in China reported fever initially, but cough first in the United States, according to researchers.

According to a new study published in PLOS Computational Biology by Peter Kuhn of the University of Southern California and colleagues, the most likely order of symptoms that COVID-19 patients experience varies depending on the viral variant.

Based on data from the initial outbreaks in China in early 2020, the researchers built a mathematical model that predicted the order of COVID-19 symptoms.

In this new study, the team wanted to see if the order of symptoms varied in people from different geographical regions or with various patient characteristics.

They employed their modeling approach to forecasting symptom order in 373,883 patients from January to May 2020 in the United States.

Surprisingly, the most common symptom order was different between the first outbreak in China, where fever was the most common symptom, followed by cough, and nausea/vomiting and the subsequent spread to the United States, where cough was the most common symptom followed by fever and diarrhea.

By reviewing additional data from Brazil, Hong Kong, and Japan, the team demonstrated that the varied ordering of symptoms was associated with SARS-CoV-2 variants, not geographic region, weather, or patient characteristics.

Cough being the first COVID-19 symptom observed by patients was linked to the presence of the D614G mutation in an area (which was prevalent in the United States in early 2020). The symptom order shifted as Japan moved away from the original Wuhan reference strain and toward the D614G strain.

The authors stress that the increased transmission of D614G is due to the symptom order.

“These findings indicate that symptom order can change with mutation in viral disease and raise the possibility that D614G variant is more transmissible because infected people are more likely to cough in public before being incapacitated with fever,” they concluded.

Source: 10.1371/journal.pcbi.1009629

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