There are some patients with novel coronavirus pneumonia who were discharged from the hospital with negative pharyngeal swabs, but when they were retested, they had positive anal swabs. Is it still contagious?
On February 24, Gong Sitang, Vice President of Guangzhou Women's and Children's Medical Center, revealed in a media interview that the first pediatric patient discharged from the hospital was discharged with 2 negative pharyngeal and anal swabs, but when he went home for isolation, the relevant personnel found, when they visited the hospital, that the anal swab was positive again.
Previously, it was also reported in the media that Guangzhou Eighth People's Hospital also had a few patients who were discharged with positive anal swab nucleic acid test results.
The reason for this phenomenon is unclear, Gong said.
If the anal swab is positive for nucleic acid, is there a live virus? How virulent is it? Is it infectious? How contagious? These are still unknown. However, as soon as they are found, they are promptly isolated.
In fact, this is not the first time a similar situation has arisen.
In Chongqing Municipal Government on February 5, the epidemic prevention and control work routine press conference. Xia Pei, deputy secretary of the party committee of Chongqing Municipal Health and Wellness Committee, had said that there have been several cases of negative throat swab test and finally positive diagnosis through anal swab in Chongqing, and asked the public to be alert to the risk of fecal-oral transmission and maintain cleanliness and hygiene. And a similar situation has occurred in Zhejiang.
What is a pharyngeal swab and what is an anal swab?
Pharyngeal swabs are taken from the nose, throat, tonsils and other parts of the body to test for viruses. A positive pharyngeal swab for nucleic acid indicates the presence of a viral gene fragment or virus in the throat or respiratory tract.
In contrast, anal swabs are taken by inserting a sampling swab 2 to 3 cm into the anus to take a specimen, or by swabbing in the folds around the anus to take a sample
A positive nucleic acid test indicates the presence of a viral gene fragment or virus in the patient's stool sample. Previously, Academician Zhong Nanshan's team has cultured a live novel coronavirus in stool, indicating that stool is infectious.
Be alert to fecal detoxification and beware of fecal-oral transmission!
On February 20, 2020, the Fifth Hospital of Sun Yat-sen University led an article published on medRxiv in which viral nucleic acid (RNA) testing was performed on the stools of 73 patients with novel coronavirus infection and found that 53.42% of patients tested positive for viral RNA in stool. 23.29% of patients were negative for viral RNA in the respiratory tract but still positive in stool. As of the time of writing, the presence of virus in the stool had been detected for a period of time lasting from 1 to 12 days.
In addition, viral RNA was detectable in gastrointestinal tissues, and further examination revealed positive immunofluorescence staining for viral envelope proteins in gastrointestinal epithelial cells. The results of this study surface that novel coronaviruses can infect cells of the gastrointestinal tract and that novel coronaviruses are present in feces.
What should I do if the throat swab is negative but the anal swab is positive?
According to the requirements of the pneumonia treatment protocol for novel coronavirus infection (trial version 6) for discharge from isolation and discharge from hospital discharge criteria, the following 4 conditions need to be met.
1. body temperature returns to normal for more than 3 days.
2. significant improvement of respiratory symptoms.
3. lung imaging showing significant improvement in the absorption of acute exudative lesions.
4. two consecutive negative nucleic acid tests of respiratory specimens (at least 1 day between sampling times).
In other words, a negative pharyngeal swab is acceptable for discharge, and the 6th edition guidelines do not explicitly require anal swab testing for patients discharged from the hospital with neoconjunctive pneumonia.
In a subset of patients, a negative pharyngeal swab but a positive anal swab indicates that a small amount of virus is still present in the body and may continue to be detoxified. Moreover, there is a certain percentage of false negatives in both pharyngeal and anal swabs, and even if the test is negative, there may be a small amount of virus in the body.
It is not known how long the virus can last in the body of a patient with a new coronavirus infection. Professor Jin Dongyan of the School of Biomedical Sciences at The University of Hong Kong Li Ka Shing Faculty of Medicine suggests that the nucleic acid test may be a false negative when the disease is healed, or the viral load is reduced due to the sensitivity of the reagents and sampling and other relationships were not detected. If you want to rule out the probability of not being detected correctly, you should test the antibody at the same time, for example, the antibody has more than four times increase to enter the recovery period, the best way is to mass-produce antibody reagents as an aid to diagnosis.
The virus may stay in the body for a long time
All these results suggest to us that the new coronavirus is very cunning, and the virus may remain in the body for a longer period of time after the patient has no symptoms.
In the case of SARS coronavirus in 2003, for example, 16% to 73% of SARS patients developed diarrhea during the course of the illness, usually seen in the first week of illness. From the fifth day of illness, SARS viral RNA is detected in the stool, and the proportion of stool specimens positive for viral RNA gradually increases, reaching a peak by the 11th day of illness; viral RNA is still present in the stool of a small proportion of patients even after 30 days of illness.
Novel coronaviruses may also persist in the patient's body for a long time, and by continuing to detoxify, they become infectious. Therefore, the criteria for discharge must be very strict, and both pharyngeal and anal swabs can be tested, and they need to be negative at the same time before discharge is considered.
After discharge, you also need to self-isolate at home for 14 days and return to the hospital for a review to find out if there is still any virus left inside the body, so that everything can be done.
