The new coronavirus (Covid-19) may be evolving into a flu-like pattern and the initial symptoms are more difficult to identify, according to a paper published on the SSRN website on March 2 by scholars from the People's Hospital of Wuhan University.

By reviewing the clinical symptoms at the time of admission to the two groups of patients diagnosed at different times, it was found that the clinical symptoms of patients with the new coronavirus pneumonia are changing and becoming more subtle overall, they said.

"These clues suggest that new coronaviruses may gradually evolve into influenza-like viruses."

Significantly reduced fever in recently admitted patients

The paper, titled “Caution: clinical characteristics of COVID-19 patients are changing at admission”, was published on the website of SSRN (article link) for researchers to share their research results.

The corresponding author of the paper is Zhang Yi, associate chief physician and associate professor of the Department of Respiratory and Critical Care Medicine, People's Hospital of Wuhan University. She has also participated in the fight against the SARS epidemic.

The paper states that the study sample was taken from 89 patients diagnosed with new-type coronavirus pneumonia admitted to the hospital from January 16 to January 29. They were divided into 2 groups based on admission time.

The first group was 31 patients from January 16 to 22, and the second group was 58 patients from January 23 to January 29. The differences in clinical symptoms between the two groups of patients were compared.

The study found that fewer women were admitted before January 23, accounting for only 45.2%, but women admitted after January 23 accounted for 77.6%.

Patients admitted before January 23 had more systemic symptoms, such as fever, fatigue, muscle soreness, etc., but these symptoms were significantly reduced in patients admitted after January 23.

In terms of sputum, 32.3% of patients admitted before January 23 had sputum. After January 23, the proportion of patients with sputum on admission dropped to 6.9%.

In addition, among patients admitted before January 23, 54.2% of patients had lymphopenia, 52.4% of patients had CD3 immune cell reduction, 42.9% of patients had CD8 immune cell reduction, and 75% of patients had increased SAA These proportions are higher than those admitted to the hospital after January 23.

The study also pointed out that there were no significant differences in the symptoms of cough, nausea, diarrhea, and chest tightness.

Initially failed to be recognized by the body

Researchers say current research has found that viral load in the nasopharynx is high shortly after symptoms appear.

Theoretically, the nasopharynx was the first organ to be infected with the virus, but observations revealed that the patients in the two groups of infection rarely showed upper respiratory symptoms in the early stages of infection.

This shows that the new coronavirus that "settles" in the nasopharynx cannot be immediately recognized by the body, and the body's immune system can hardly clear it through self-cleaning reactions such as sneezing and runny nose. Therefore, the initial symptoms of the new coronavirus are hidden.

The study compared the clinical symptoms of patients admitted to the hospital with different periods of time and found that the initial symptoms of recently infected patients appear to be more subtle. "All of these provide clues that the new coronavirus may gradually evolve into an influenza-like virus, or may lie in certain asymptomatic vectors for a long time."

Researchers caution that, even if the initial symptoms of recently infected patients are more cryptic, there is no evidence that the transmission and pathogenicity of the new coronavirus has weakened during transmission, "because of the emergence of the third and fourth generations of the new coronavirus, even asymptomatic carry Therefore, it is urgent to distinguish the clinical manifestations of patients with new-type coronavirus pneumonia at different infection stages. "

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