This study included 37 RT–PCR-confirmed SARS-CoV-2 infected participants in the Wanzhou District of China. None of the 37 had any relevant clinical symptoms in the preceding 14 days and during hospitalization, and therefore were considered asymptomatic. This paper describes the epidemiological and clinical characteristics, virus levels and immune responses in 37 asymptomatic individuals from the National Health Commission of China updated COVID-19 Prevention and Control Plan.

Overall, the data suggest that asymptomatic individuals had a weaker immune response to SARS-CoV-2 infection.  "The reduction in IgG and neutralizing antibody levels in the early convalescent phase might have implications for immunity strategy and serological surveys."

Introduction for Clinical and immunological assessment of asymptomatic SARS-CoV-2 infections

- Viral shedding
- IgG levels
- Low white blood cell count (lymphopenia)
- Low blood platelet count (thrombocytopenia)
- Chest CT focal ground-glass opacities
- Chest CT stripe shadows

University of Michigan - Ann Arbor

Several studies have shown that COVID-19 can be transmitted by individuals who do not show any symptoms, or who are "asymptomatic". Because asymptomatic individuals are not routinely tested, the prevalence of asymptomatic infection is not well-defined.

Asymptomatic COVID-19 Infection

Previous reports indicate that asymptomatic transmission is possible, but since they’re hard to track, this poses a significant challenge to infection control practices.

Implications of Asymptomatic COVID-19 Transmission

- China
- Germany
- Japan
- USA
- Singapore

Asymptomatic COVID-19 Infection Categorized by Country

- Travel Medicine and Infectious Diseases References
-Science China Life Sciences
-Journal of American Medical Association (JAMA)
- New England Journal of Medicine (NEJM)
- Euro Surveillance
- Morbidity and Mortality Weekly Report (MMWR)
- Nature Medicine

Asymptomatic COVID-19 Infection References by Journal

Clinical and Immunological Results of Asymptomatic COVID-19 Infection

Due to the SARS-CoV-2 viral load being similar between asymptomatic and symptomatic healthcare workers with COVID-19, asymptomatic healthcare workers donning less PPE may be a risk factor for other colleagues, patients, and the community.

Healthcare Workers with Asymptomatic COVID-19 Infection

In addition to symptomatic screening, additional control/detection methods are routine rRT-PCR testing, conservative guidelines for reopening, and periodic testing are important for epidemiological evaluations. Facilities using these methods include nursing homes and other congregate living situations such as prisons, mental health facilities, and homeless shelters.

Additional control/detection methods to prevent asymptomatic transmission

- Fever (when high temperature is measured)
- Laboratory confirmation of illness via viral testing
- Radiological lung abnormalities such as ground-glass chest and stripe shadowing


Clinical Characteristics of Asymptomatic COVID-19 Patients

Studies have shown that even though asymptomatic people have the same viral load, they have increased levels of lymphocytes (CD4+cells) as compared to symptomatic people, which may lead to them being asymptomatic. Due to the presence of increased lymphocytes, they also clear the viral particles faster and show lower risk of long term complications. 



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