A new study by USC researchers found that the order of symptoms in the first wave of COVID-19 varied among virus variants.

The variant of the SARS-COV-2 virus that was rapidly spreading in the US and Europe during the first wave of the outbreak could have been particularly infectious because the most common early symptom was likely a cough, according to a new study.

People infected with COVID-19, which was the world’s most infectious strain in May 2020 and the most prevalent strain in the United States two months later, were more likely to develop a cough as their initial symptom, followed by a fever, according to the study.

The study was carried out at the USC Michelson Center for Convergent Bioscience, which is part of Peter Kuhn’s Convergent Science Institute in Cancer.

Infected people coughing and spreading the virus before becoming disabled by fever could explain the higher transmissibility of that strain — D614G. COVID-19 is most typically transmitted through respiratory droplets, which are often increased by symptomatic individuals’ coughs.

Those infected with the COVID-19 strain, the Wuhan reference strain, during the initial outbreak in China, had fever as their first symptom, followed by cough.

Additional research and health care regarding how patients experience the disease can be guided by studying the likely order of symptoms, as well as how the disease spreads.

The report, which was published in PLOS Computational Biology today, also found:

• When the Wuhan reference strain was dominant in Japan, a fever was most commonly the first sign. Cough was most likely the initial symptom when the D614G mutation took root. This observation backs up comparable findings from other places, and it supports the theory that the D614G variation coughs earlier than the Wuhan reference strain.
• Region, weather, patient age, or comorbidity had no effect on the expected symptom sequence.
• The study did not address whether the order of symptoms observed in the early waves of the pandemic is still valid for contemporary variations.

“With the emergence of new variants and the likelihood COVID-19 becomes endemic in the population, it’s important that researchers continue to show how viral variants affect progression of symptoms and disease in individuals and populations,” said Professor Peter Kuhn.

“Studying the likely order of symptoms may increase our understanding of how disease spreads and further inform future research and health care on how individuals are likely to experience disease,” added graduate researcher Joseph Larsen.

Source: 10.1371/journal.pcbi.1009629

Image Credit: Getty

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