Covid-19: Asymptomatic people are more contagious than previously thought
People with coronavirus but no symptoms appear to have similar levels of the virus in the nose and throat as people with mild symptoms, a study found.
While this does not necessarily mean that the latter are as likely to be contagious as sick patients, researchers are concerned that they may still contribute to the spread of SARS-CoV-2, hence the importance of testing for gestures of protection and barrier.
The issue of transmission of SARS-CoV-2 by an asymptomatic person is particularly important today, in order to better adapt prevention and control measures against the Covid-19 epidemic. Therefore, many scientific teams are trying to find out if a person with SARS-CoV-2 who does not have symptoms can excrete viral particles. If so, are they as contagious as sick people? The stakes in these questions are important because if not isolated, these people can unknowingly transmit the virus to other people who may develop a sometimes severe clinical form of the disease.
A new study by researchers at the Ulsan University School of Medicine, South Korea, and published in the journal Thorax reveals that people with a "silent" infection or "healthy carriers" have the same amount of viral load in the nose and throat than those showing symptoms. Given the large number of these people, a fifth of those infected, according to the study results, these healthy carriers can therefore play a key role in the spread of Covid-19. Therefore, people infected with SARS-CoV-2 but showing no symptoms still have a high enough viral load to be dangerous.
Determine the presence of viral load in healthy carriers.
But as the researchers explain, "it was not clear the extent of this viral load and to what extent it could contribute to the spread of the virus." To shed some light on this, they compared the viral load (amount of virus present in circulating blood) of 213 people who tested positive for SARS-CoV-2, but not all showed symptoms of infection. After a major Covid-19 epidemic in the city of Daegu, South Korea, at the beginning of the pandemic, contact cases of these people were found, leading to the discovery of more than 3,000 cases of Covid-19, the severity of which of symptoms ranged from "none" to "severe".
People with mild or no symptoms were admitted to specialized care centers for isolation and follow-up. They were classified as asymptomatic if they did not present any of the following symptoms: fever, chills, muscle pain, fatigue, runny or stuffy nose, loss of taste or smell, sore throat, difficulty swallowing, cough, headache, dizziness, loss appetite, nausea, vomiting, abdominal pain and diarrhea. Before the isolation period, 41 people did not develop any symptoms. Then 39 of them underwent another nose and throat sample test 13 days after their initial diagnosis.
"An Essential Driving Force for the Spread of Covid-19"
Of the other 172 people with mild symptoms, 144 were reexamined, for a total of 183 people included in the final analysis. It turns out that more than half of the people without symptoms were still positive for the virus, as were nearly two-thirds of those with mild symptoms, but there was no significant difference in the amount of viral RNA detected between the two groups. While more work is needed to confirm these results, the researchers believe their finding reinforces the hypothesis already presented in many other studies that asymptomatic people can spread the virus.
"Given that the majority of asymptomatic people with Covid-19 are likely to go unnoticed by healthcare workers and continue to reside in communities, these individuals can act as a critical driving force for the spread of the disease in the community. Covid -19 ", they explain. The next step now is to determine precisely how long and to what extent asymptomatic people are contagious, in order to establish appropriate quarantine rules for them. Meanwhile, these results confirm the importance of social distancing and the use of masks.
"Our data reinforce the recommendation to wear masks regardless of the presence of symptoms and suggest that the detection of SARS-CoV-2 should include asymptomatic people who work in high-risk settings, such as nursing homes," concludes the lead author. of the study, Professor Sung-Han Kim. Based on the results obtained, he confirmed that there are many perSons in which virus shedding is demonstrated by nasopharyngeal swabs, before symptoms develop or even without developing them.