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Many individuals show subclinical abnormalities as well as differences from symptomatic patients
by Molly Walker, Associate Editor, MedPage Today June 18, 2020
Asymptomatic individuals carrying SARS-CoV-2 shed the virus longer than those with COVID-19 symptoms, with other lab findings suggesting the symptomatic patients mounted more robust immune responses, a small study in China found.
Median duration of viral shedding among 37 asymptomatic patients was 19 days (interquartile range 15-26; range 6-45) versus 14 days among 37 matched symptomatic patients (IQR 9-22; log-rank P=0.028), reported Jing-Fu Qiu, PhD, of Chongqing Medical University, and colleagues, though viral shedding does not necessarily mean the patients were infectious.
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Asymptomatic individuals carrying SARS-CoV-2 shed the virus longer than those with COVID-19 symptoms, with other lab findings suggesting the symptomatic patients mounted more robust immune responses, a small study in China found.
Median duration of viral shedding among 37 asymptomatic patients was 19 days (interquartile range 15-26; range 6-45) versus 14 days among 37 matched symptomatic patients (IQR 9-22; log-rank P=0.028), reported Jing-Fu Qiu, PhD, of Chongqing Medical University, and colleagues, though viral shedding does not necessarily mean the patients were infectious.
Virus-specific IgG antibody titers and cytokine levels were also significantly lower among asymptomatic patients in the acute phase of infection, when viral RNA can be found in respiratory specimens, the authors wrote in Nature Medicine — both of which indicated that immune responses weren’t as strong in the asymptomatic group.
Asymptomatic transmission of COVID-19 is one of its biggest mysteries, with the World Health Organization recently reminding the public of the distinction between asymptomatic patients, who never develop symptoms, and presymptomatic patients, who go on to develop symptoms later in the course of disease.
Qiu and colleagues characterized asymptomatic carriers as the “silent spreaders” of COVID-19.
“However, our understanding of the clinical features and immune responses of asymptomatic individuals with SARS-CoV-2 infection is limited,” the researchers added.\
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These findings should serve as a caution against assuming prior infection confers immunity to future infection, Qiu and colleagues said.
“These data might indicate the risks of using COVID-19 ‘immunity passports’ and support the prolongation of public health interventions, including social distancing, hygiene, isolation of high-risk groups, and widespread testing,” the team wrote.
Plasma levels of cytokines were also similar between asymptomatic patients and healthy controls, though significantly higher levels of stem cell factor and leukemia inhibitory factor were found in the asymptomatic group, the researchers noted, calling this a “reduced inflammatory response characterized by low circulating concentrations of cytokines and chemokines.”
Qiu and co-authors cited the varying sensitivity and specificity of antibody tests (obtained from a company called Bioscience) as a limitation to their study, adding that the results may be confounded by existing antibodies to other coronaviruses, such as SARS or MERS, as well as common cold viruses.Last Updated June 18, 2020
https://www.medpagetoday.com/infectiousdisease/covid19/87168
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Asymptomatic spread of coronavirus is ‘very rare,’ WHO says
PUBLISHED MON, JUN 8 20201:05 PM EDTUPDATED 27 MIN AGO
William Feuer@WILLFOIA
Noah Higgins-Dunn@HIGGINSDUNN
POINTS
Government responses should focus on detecting and isolating infected people with symptoms, the World Health Organization said.
Preliminary evidence from the earliest outbreaks indicated the virus could spread even if people didn’t have symptoms.
But the WHO says that while asymptomatic spread can occur, it is “very rare.
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