The decrease in the number of confirmed cases of new coronary pneumonia in China is gratifying, but the number of “asymptomatic infections” cannot be ignored. Recently, studies of asymptomatic infections have appeared frequently in well-known medical journals, including NEJM, JAMA, medRxiv, and so on. The latest study, led by Shen Hongbing, a member of the Chinese Academy of Engineering and deputy secretary of the Party Committee of Nanjing Medical University and president, points out that the infection of asymptomatic infected people with the new coronavirus can last up to 29 days.
First reported asymptomatic new coronavirus infection
On February 18, 2020, NEJM published a newsletter about Evidence of SARS-CoV-2 Infection in Return Travelers from Wuhan, China (SARS-Infected among Travelers Returning from Wuhan, China) CoV-2 evidence), reporting on the screening of the new coronavirus for 126 personnel evacuated from Hubei by a German Air Force aircraft.
In addition to the planned steps of infection signs and symptom tests, and asymptomatic queue observation in quarantine, the researchers decided to provide 115 travelers with a pharynx swab test for SARS-CoV-2, with a total of 114 passengers agreeing to be tested, the paper said. Two of the 114 travellers (1.8%) tested positive for SARS-CoV-2 (the cycle thresholds for both samples were 24.39 and 30.25, respectively).
The researchers then used two market-based kits (LightMix Illo and Wuhan CoV E-gene and LightMix Wuhan CoV RdRP-gene, both produced by TIB MOLBIOL) to positive samples A second test was carried out, and a positive sample was tested again at the Institute of Virology at Philipps University Marburg in Germany, confirming the positive results.
In addition, IN CACO-2 CELL CULTURE, SARS-CoV-2 was isolated from both samples, indicating potential contagion.
That is to say, the above 2 travelers have no clinical symptoms, virological testing is positive, and this also just in line with China’s new coronary pneumonia treatment program in the fifth and fourth version of the treatment of asymptomatic infection synosymptoma.
The viral load of asymptomatic patients is similar to that of asymptomatic patients
In fact, in the case of asymptomatic infections, NEJM subsequently published another newsletter.
On February 19, 2020, NEJM published a newsletter by the Guangdong CDC, Zhuhai CDC, Sun Yat-sen University Affiliated Fifth Hospital, The University of Hong Kong and other research institutions. The researchers monitored 18 patients (9 males and 9 females, 4 of whom were secondary cases and 1 had no symptoms) in 18 upper respiratory tract samples (nose swabs, pharynx swabs) in Zhuhai, Guangdong Province, using the new coronavirus nucleic acid determination kit (real-time fluorescence RT-PCR method) provided by the CDC SARS-CoV-2 virus load.
The asymptomatic infected persons mentioned above have been in close contact with the confirmed cases and, although there are no clinical symptoms, the nasal swabs (cycle threshold 22-28) and laryngeal swabs (cycle threshold 30-32) tested positive for the 7th, 10th and 11th days after close contact.
At the same time, the viral load detected in respiratory samples of asymptomatic patients was similar to that of asymptomatic patients – indicating that asymptomatic patients also had the potential to spread, thus confirming earlier conclusions about asymptomatic infections.
Asymptomatic infections up to 29 days
Based on this, the researchers analyzed a group of asymptomatic infections.
On February 25, 2020, the Shen Hongbing Fellows team of Nanjing Medical University published a copy of the pre-printed website medRxiv entitled Clinical Features of 24 Asymptomatic Infections with COVID-19 Sc Reened Access Contacts in Nanjing, China (clinical characteristics of 24 patients with close contact with asymptomatic infections in patients in Nanjing).
It is reported that through the pharynx swab nucleic acid test, 24 asymptomatic patients are positive for COVID-19 virus. The team analyzed their clinical records, laboratory assessments, and chest CT scan results.
The paper notes that the median time between the first nucleic acid test positive to the two consecutive tests for transnegative is 9.5 days, during which time they also have the potential to spread – asymptomatic patients have been infected with their families, and some infected people have developed severe illness.
According to the team analysis, 24 asymptomatic infections are mainly divided into two categories – one is the family of the patient, and the other is less than two meters away from the patient sined by the latent period, contact time of more than an hour. Furthermore, 8 out of 24 people have a history of hubei travel (see chart below).
It is worth mentioning that most of the symptoms of the 24 people were mild and did not develop to serious illness. However, there were 6 asymptomatic infections that went to yang after a nucleic acid test was negative, and 1 case even after consecutive negatives.
Patient No. 13 is in a special condition – after infecting a family member and having been diagnosed with it, he has not developed symptoms. Until February 18, the patient’s nucleic acid test was not transotorioned, meaning that his infection could last up to 29 days.
Based on the above analysis, the team highlighted the importance of tracking close contact with confirmed patients and longitudinal monitoring using viral nucleic acid testing.
In fact, there has been a lively discussion about asymptomatic infections.
Some netizens with relevant backgrounds said that this is due to the new coronavirus “bullying and hard” – asymptomatic infected people (similar to typhoid Mary) immunity is strong, and the new coronavirus is weak, but if the virus is transmitted to the weak immunity of the host, it may cause severe illness.
The source is known for the “Yumi Group”
However, as mentioned above, most of the asymptomatic infections found so far are in close contact with the confirmed patient, so we need not be too alarmed. But at the same time, the virus is ferocious, not to be underestimated.