6Comments
The different COVID-19 variants spread at different rates and have different levels of danger. Now it looks like they also have different orders of symptoms, which could help identify which variants people have and provide insights into how SARS-CoV-2, the virus responsible for COVID, spreads.
In a paper published in PLOS Computational Biology, researchers looked at variations of symptoms across thousands of people. They were interested to know if patient characteristics, geographic location, and even weather might affect symptoms. The data shows that actually, it’s all down to the variants.
In the original version of the virus, first identified in Wuhan, the first symptom was fever, then the infamous "new and continuous" cough, with the third most common symptom being nausea/vomiting. However, the first variant that became dominant across the world in the early months of 2020, D614G, had coughing as the first symptom, followed by fever, and thirdly by diarrhea.
The fact that coughing came first with D614G might explain why it spread so quickly, the researchers say. People with a cough would likely still be out and about spreading the virus before the fever would force them to stay home. This allows a variant to become dominant.
In their study, the team looked at the symptoms originally described in the initial cases from the first outbreak in China. They then used a modeling approach to establish the most likely symptom order among a set made of 373,883 cases in the USA between January and May 2020, when D614G became dominant.
They analyzed additional data from Brazil, Hong Kong, and Japan, including symptom order and dominant variant during those time frames. Their findings showed that COVID symptoms depend principally on the SARS-CoV-2 variant and that external factors like geographic region, do not come into play.
“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,” lead author Joseph Larsen, a graduate researcher at the University of Southern California (USC, said in a statement.
“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 the progression of symptoms and disease in individuals and populations,” added senior author Peter Kuhn, Dean’s Professor of Biological Sciences at USC.
Scientists across the world have been approaching symptoms as a way to understand some crucial mechanics of the disease. The ZOE COVID-19 symptoms study, for example, continues to highlight differences in what the variants lead to, including the different symptoms seen in people who have contracted the Omicron variant.
