Unconscious spread: the characteristic of the Delta variant that makes it more contagious than others

Since its first identification in October 2020, the Delta variant started to gain traction around the world. Today, it is present in more than 140 countries and modified strategies before the pandemic. Now a study published in the journal Nature, which has no peer validation, found that people infected with this mutation of the Covid-19 They are contagious for up to 48 hours before showing symptoms, thus doubling the sale of unconscious spread.

“Infected people Delta variant of SARS-CoV-2 are more likely to spread the virus before they develop symptoms than people infected with previous versions, ”says a study of an outbreak in Guangdong, China.

Based on analysis of 101 people infected between May and June 2021, this research indicated that, on average, those who were infected with this variant started showing symptoms 5.8 days after contracting the disease.

That is, the symptoms appeared in a on average 1.8 days after testing positive in the PCR test. So the unconscious spread window of the disease, because people feel well and do not show signs of the disease, it has been localized almost two days.

“It’s harder to stop it,” said Benjamin Cowling, epidemiologist at the University of Hong Kong and co-author of the study published in the prestigious scientific journal. Nature and still awaiting peer review.

Likewise, Cowling noted that they analyzed the unconscious spreading windows of the other variants in a study they had previously conducted but have not published.

“Before the emergence of the Delta variant, people infected with SARS-CoV-2 took, on average, 6.3 days to develop symptoms and 5.5 days to test positive for PCR. With which, the the unconscious viral shedding window was 0.8 days“said the researcher.

In addition, scientists have successfully detected that people infected with the Delta variant here higher concentrations of virus in viral particles or viral load.

The researchers also pointed out that 74% of Delta infections occurred during the presymptomatic phase. “These data help explain how this variant was able to outperform both wild-type (parent) virus and other variants to become the dominant strain globally,” said Barnaby Young, infectious disease physician at National. Center for Cancer. .

According to scientists’ estimates, the R 0 of the Delta, a number which makes it possible to calculate the degree of contagiousness of a pathogen by analyzing the average number of susceptible people that each infected person infects, are at 6.4, much higher than 2-4 of the previous mutations.

To put it simply, if a person’s original virus “jumps” to two and two to four, in The one-person Delta variant spreads to almost 6 1/2 people, who will end up infecting around 42.

“The Delta moves a little faster, but it’s much more transmissible,” said Marm Kilpatrick, an infectious disease researcher at the University of California, Santa Cruz.