Asymptomatic people spread the virus in more than half of the cases, and the CDC model

In the model baseline scenario, 59% of all infections came from asymptomatic individuals. This includes 35% of new cases from people who have been infected with others before they have symptoms and 24% from people who have never had symptoms.

“The bottom line is to control the pandemic of covid-19. In reality, we need to control the silent pandemic of infections from asymptomatic individuals,” he said. Jay C. Butler, Deputy Director of CDC for Infectious Diseases, and co-author of the study. “A community mitigation tool that we need to make widespread to be able to delay the spread of SARS-CoV-2 from all infected individuals, at least until these vaccines are widely available. “

Appearance of More contagious variantsHas cast the importance of these guidelines into even more serious remedies since it was first detected in the United Kingdom and discovered in several states in the United States. “These findings are currently in bold, italic, and underlined,” Butler said. “I changed from an 11-point font to a 16-point font.”

“It’s a confirmation, but it’s nice to see the confirmation,” the epidemiologist said. Richard MenziesDirected the McGill International Tuberculosis Center in Canada and had nothing to do with this study. “These are pretty reliable and solid results.”

Many factors affect the spread of the coronavirus. Researchers have clearly taken a simple approach, which Butler calls a “pretty simple mathematical model” and uses it to determine the duration of infection and the rate of infection from people who have never developed symptoms. We changed and evaluated some scenarios.

The model consistently predicted asymptomatic spread and accounted for about half of viral infections. “I was a little surprised at how well it was maintained under a wide range of basic assumptions,” said Butler, shifting the timing of peak infections from four days to five to six days after infection.

But Huge sevicInfectious disease experts at the University of St Andrews in Scotland claimed that some of the model’s assumptions were flawed. Cevik has a best estimate of 35% relative infectivity between asymptomatic and symptomatic individuals. Review of scientific literature Published in September.

Instead, the authors of the study estimated at baseline that asymptomatic people were 75 percent contagious. According to Butler, the numbers come from a unique literature analysis that includes peer-reviewed and preprinted studies. “Still, there is no doubt that people will ask,” What if I do X, Y, Z? ” But hopefully, being able to adjust the variables will help address some of those concerns, such as what we did, “Butler said.

Cevik also stated that the study did not consider the environment in which diffusion occurs. “Asymptomatic carriers may be important, but more important in long-term care facilities and homes,” she said. “It may mean that high-risk populations need to be tested much more targeted, as opposed to mass screening.”

Whether the vaccine blocks coronavirus infection is not yet clear and was not the scenario featured in this model. “Data on the effects of vaccines on asymptomatic infections are very limited,” Butler said, but expects more information in the coming months.

In a clinical trial of an mRNA vaccine approved in December, vaccination was concluded as follows: Very competent To prevent symptomatological illness. However, these trials did not determine whether vaccinated people could spread the pathogen.

“If they are asymptomatic but equally contagious, it will have a significant impact on the epidemic,” Menzies warned. That’s why it’s so important to keep testing people, especially those who have been vaccinated and then exposed to the virus, he said.