Today, the journal Nature published a paper detailing the virological characteristics of the new coronavirus in a group of hospitalized patients. Once the paper was launched, it caused a stir on social media overseas. Some comments noted that the work was excellent and provided very important data.
From a virological point of view, it not only reveals many differences between the new coronavirus and SARS virus, but also strongly supports the view that “asymptomatic people are infected”, and re-emphasizes the significance of doing a good job of protection based on the “all people are potential lying”.
It’s worth noting that this paper is available in the form of “accelerated article preview”. Readers will also be able to read this important work before specific typography and proofreading work (click on “Read the original/Read More” at the end of the article).
The paper came from a German team and the samples used in the study were from nine patients in Munich. Samples of swabs or nasopharyngeal swabs from these patients date back to the first day of symptoms, the researchers note. At this point, their symptoms are often very mild. It is important to note that during the first 5 days of symptoms, the patient’s swabs were positive and the RNA levels of the new coronavirus were high. In addition, in the patient’s sputum, the researchers also detected RNA from the new coronavirus.
Theoretically, the ability to detect the virus’s RNA does not mean that the virus is still alive (dead viruses also have viral RNA). To determine whether a patient is potentially contagious when he or she first develops symptoms, the scientists further tried to isolate and culture the virus from the patient’s sample. Subsequent results showed that during the first week of symptoms, both the patient’s swabs and sputum samples were able to isolate the virus. From day 8, scientists were never able to isolate the virus, even though a higher viral load was detected in the patient’s sample.
Based on these results, the researchers speculate that the virus replicates in the upper respiratory tract early in the course of the disease. To test this idea, they designed a special test to specifically detect the virus’s sgRNA, a special RNA that can only be found in infected cells, indicating the viral replication activity. The results showed that the new coronavirus could replicate actively in the pharynx during the first 5 days of symptoms.
The virus can be isolated in both pharynx (yellow) and sputum samples (orange). The virus cannot be isolated from stool samples (grey) (Photo: Resources)
Previous studies have shown that large amounts of viral RNA have been detected in patients’ stool samples. Does this indicate that the virus may also be transmitted through the dung? To answer this question, the researchers also analyzed the patient’s feces. The results showed that although the level slotted by the new coronavirus RNA in the feces was very high, the virus could not be isolated from 13 samples tested. In addition, using this technique to detect virus replication, the researchers did not observe significant virus replication in the feces. In general, in order to reduce infection, prevention and control means should be focused on reducing the spread of droplets.
In other studies, scientists have also found some strange features of the new coronavirus. They noted that six of the nine patients had stool and sputum samples that could still detect RNA from the new coronavirus after three weeks. By this point, their symptoms had already disappeared. Given that medical resources are still scarce today, many hospitals will choose to get patients out of the hospital as soon as possible. The authors say that when we discharge patients, we need to follow strict criteria (e.g. 10 days after the onset of symptoms, or no more than 100,000 copies of the virus per milliliter) to minimize risk.
After the symptoms disappear, viral RNA can still be detected in the patient’s sputum sample (orange) and stool sample (grey) (Photo: Resources)
In the summary part of the paper, the researchers point out that in the patients analyzed, the new coronavirus and SARS virus exhibited very different virological characteristics. In the case of SARS viruses, RNA levels typically peak 7-10 days after symptoms appear. The new coronavirus appears to be “the pinnacle” and RNA levels peak within 5 days of the onset of symptoms. And compared to SARS virus, the peak can be 1000 times higher! In addition, they were surprised to be able to isolate the new coronavirus from a pharynx sample. In contrast, the isolation of SARS virus has been rarely successful.
Taken together, these results suggest that the new coronavirus can replicate actively in upper respiratory tissue and reach a high level when symptoms are not obvious. By the time the patient develops symptoms, the virus’s peak in the upper respiratory tract may even be over. To this end, in order to control the new corona lepidemic, we need more stringent and effective means than the fight against SARS virus.