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People infected with the delta variant of the new coronavirus could carry a thousand times more virus particles and may test positive two days earlier than those infected with the original SARS-CoV-2, according to a new study. The study was not peer-reviewed and only looked at a small number of cases in China, but if the results can be confirmed, they could explain, at least in part, why the delta variant is so more contagious.
The delta variant has now spread to more than 100 countries and currently accounts for 83% of new COVID-19 cases in the United States, with a particularly high number of cases in areas with low vaccination rates, Previously reported live science. This variant is believed to be 60% more transmissible than the previous dominant strain and twice as infectious as the original strain of SARS-CoV-2.
While it’s clear that delta is very good at spreading quickly, researchers aren’t sure why. To better understand, a group of researchers in China studied how the delta variant spread from the first known local transmission identified on May 21. The authors published their results as a preprint study on Virological July 7.
Related: Coronavirus Variants: Here’s How SARS-CoV-2 Mutants Stack Up
China’s Guangdong and other local centers for disease control and prevention have carried out surveillance and testing of people infected with the delta variant and their close contacts in China. Close contacts of infected people have been isolated and passed daily COVID-19 polymerase chain reaction (PCR) tests. Authorities have identified 167 local infections that date back to the original index case.
They compared the data from these people with data from the early days of the pandemic, when the original SARS-CoV-2 was spreading in China.
They found that the average time it takes between a person’s exposure to the virus and testing positive for PCR tests (or the time it takes for the virus to replicate at levels high enough to be detectable) was 5.61 days. for the original virus and 3.71 days. for the delta variant.
The most “striking” aspect of this report was that it takes much longer to be exposed to the delta variant to show significant levels of the virus, said John Connor, a researcher at the National Emerging Infectious Diseases Laboratories of the Boston University who was not involved in the study. It changes the “window” of when people are contagious, Connor told Live Science.
“As we know, individuals experience a latency period after infection, during which the viral titers [concentrations] are too weak to be detected. As viral proliferation continues in [the] host, the viral load will eventually reach a detectable level and become infectious, ”the authors wrote in the study. “Knowing when an infected person can spread viruses is essential for designing intervention strategies to break the chains of transmission. In other words, contact tracing should work faster to prevent people from transmitting the delta.
The researchers also measured viral loads when SARS-CoV-2 was first detected in PCR tests. They found that the viral loads in the delta-variant infections were 1,260 times higher than those in the original viral infections. This suggests that the delta variant may replicate in the body at a faster rate than the original virus.
“These data show that the delta variant may be more infectious at the onset of infection,” the authors wrote. This, in turn, suggests that the person would shed more virus particles, which would increase the risk of transmission.
Still, the higher replication rate may not fully explain why delta is so efficient, and “there are a lot of unanswered questions,” Connor added. For example, it would be important for future studies to understand how infectious the detected virus is, he said.
Originally posted on Live Science.
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