Asymptomatic COVID-19 infection: diagnosis, transmission, population characteristics

Abstract

A novel coronavirus first discovered in late December 2019 has spread to many countries around the world. An increasing number of asymptomatic patients have been reported and their ability to spread the virus has been proven. This brings major challenges to the control of the transmission. The discovery and control of asymptomatic patients with COVID-19 are the key issues in future epidemic prevention and recovery. In this narrative review, we summarise the existing knowledge about asymptomatic patients and put forward detection methods that are suitable for finding such patients. Besides, we compared the characteristics and transmissibility of asymptomatic patients in different populations in order to find the best screening, diagnosis and control measures for different populations. Comprehensive preventive advice is also provided to prevent the spread of infection from asymptomatic patients.

Comparison of the Characteristics of Asymptomatic and Presymptomatic Patients with Coronavirus Disease 2019 in the Republic of Korea

“…The proportion of asymptomatic infections with COVID-19 varied between studies, depending on the country, medical institution, the tested group, patient epidemiology, and intensive surveillance [ 7 , 8 , 10 , 17 , 18 ]. In a review article on COVID-19, it was reported that the proportion of asymptomatic patients during COVID-19 was about 4%, but in this study, it was about 22% [ 19 ]. This is thought to be due to more intensive surveillance in Republic of Korea than in other countries.…”

“…According to studies published so far, asymptomatic COVID-19 patients were younger and had fewer underlying diseases, and chest CT was more often normal. In addition, patients with pre-symptomatic COVID-19 were more likely to be elderly, have hypertension, have abnormal findings on chest CT, especially with consolidations [ 19 , 20 ]. We found that pre-symptomatic patients had more underlying diseases.…”

Relevance of Cycle Threshold Values in Mass Screening by Reverse-Transcription-PCR During COVID-19 Pandemic in Belgium: A Decision-Making Support?

“…A meta-analysis reported that 15.6% of positive individuals are asymptomatic at initial diagnostic among which 51.1% will remain asymptomatic [ 7 ]. Virus can be transmitted by droplets, aerosol and conjunctiva and studies showed that viral load of respiratory samples were similar in asymptomatic and symptomatic patients [ 8 , 9 ]. Transmission potential of asymptomatic individuals seems to be lower than those of symptomatic patient but still substantial [ 8 , 10 ].…”

“…Virus can be transmitted by droplets, aerosol and conjunctiva and studies showed that viral load of respiratory samples were similar in asymptomatic and symptomatic patients [ 8 , 9 ]. Transmission potential of asymptomatic individuals seems to be lower than those of symptomatic patient but still substantial [ 8 , 10 ]. Therefore, Sciensano’s recommendation to interpret Ct values should be cautious and as general as possible in order to identify and isolate the most contagious patients.…”

Telemedicine and artificial intelligence to support self-isolation of COVID-19 patients: Recent updates and challenges

“… 2 In practice, asymptomatic and high-risk patients self-isolate at home and are expected to call their doctor if their condition worsens. 3 , 4 However, patients can begin to deteriorate without notice, and by the time they realize that something is mistaken, the chance for early life-saving treatment may have been missed. 4 Based on the issue, it is necessary to develop methods to communicate efficiently with asymptomatic and high-risk COVID-19 patients under self-isolation at home.…”