COVID-19 remains stubbornly inconsistent. More than a million people have died and 35 million have been diagnosed, but a large fraction of people infected with the coronavirus--about 45%, according to recent estimates--show no symptoms at all. A retrospective study of 52 COVID-19 patients, published online on October 7, 2020 in mSphere, an open-access journal of the American Society for Microbiology, may help researchers better understand why not everyone show symptoms of the disease. The article is titled “Descriptive, Retrospective Study of the Clinical Characteristics of Asymptomatic COVID-19 Patients.” The study's authors found that asymptomatic patients hosted viral loads comparable to those of symptomatic patients, but asymptomatic patients showed higher levels of lymphocytes (a type of white blood cell responsible for immune responses), cleared the viral particles faster, and had lower risks of long-term complications. Further analyses suggested the interaction between the virus and the immune system likely played a role in that process. "Our findings suggested an important role for lymphocytes, especially T-cells, in controlling virus shedding," said virologist Yuchen Xia, PhD, at Wuhan University's School of Basic Medical Sciences in China, senior author of the new study. The wide range of COVID-19 symptoms is well documented. Asymptomatic carriers, on the other hand, often go undiagnosed, but can still shed the virus and spread it to others. Understanding why some patients get sick and others don't is one of the most important challenges in curbing the pandemic, Dr. Xia said. "They may cause a greater risk of virus transmission than symptomatic patients, posing a major challenge to infection control." Dr.
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