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Cough or fever first? Covid variants can make symptoms appear in different order, US study says

Symptom order can change with mutations in the virus, finds a study by researchers from the University of Southern California, published in 'PLOS Computational Biology'.

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New Delhi: The order of the symptoms that Covid-19 patients experience can differ with variants of the virus, according to a new study that explains how such changes can impact the spread of the infection. 

In the study published in the journal PLOS Computational Biology, researchers from the University of Southern California in the US sought to find out whether the order of symptoms varied in patients from different geographical regions or with various patient characteristics.

The team had previously developed a mathematical model predicting the order of Covid-19 symptoms based on data from the initial outbreak in China in early 2020.

In the new study, they used their modelling approach to predict symptom order in a set of 373,883 cases in the US between January and May 2020.

They found that the most likely symptom order differed between the initial outbreak in China — where fever most often preceded a cough, and nausea was a common third symptom — and the spread to the US.

In the US, a cough was most likely to be the first symptom, and diarrhoea was a more common third symptom.

Orders of symptoms associated with variants

By analysing additional data from Brazil, Hong Kong and Japan, the team found that the different orders of symptoms were associated not with geographic region, weather, or patient characteristics, but with SARS-CoV-2 variants. 

The presence of the D614G mutation — one of the earliest identified spike protein mutations of SARS-CoV-2 —  was associated with a higher likelihood of a cough being the first Covid-19 symptom experienced by patients. 

As Japan shifted from the original Wuhan reference strain to the D614G variant, symptom order shifted as well. The team hypothesised that the increased transmission of D614G could be linked to the symptom order.

(Edited by Rohan Manoj)

Also read: If antibodies fail, T cells in Covid-recovered people could shield from Omicron, says US study


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