Researchers in China said people with the SARS-CoV-2 delta strain are more likely to spread the virus before symptoms appear. They compared this figure with people who became infected with early versions of the coronavirus.
“It’s just harder to control,” said Benjamin Cowling, an epidemiologist at the University of Hong Kong and co-author of the study.
Cowling and his colleagues analyzed data from 101 patients in Guangdong who contracted the delta strain between May and June 2021, as well as data from close contacts of these people. They found that, on average, people began to experience symptoms 5.8 days after being infected with the new strain – 1.8 days after they first tested for viral RNA. Thus, people had almost two days to transmit the virus before they showed signs of COVID-19.
Prior to the onset of the delta, earlier research and unpublished analysis showed that people infected with SARS-CoV-2 took an average of 6.3 days to develop symptoms and 5.5 days to test positive for viral RNA, leaving a narrower window of time. at 0.8 days for the virus to spread without a trace.
In the latest work, the researchers also found that people infected with the delta strain had a higher concentration of viral particles in the body than people infected with the original version of SARS-CoV-2. “Somehow the virus appears faster and in greater numbers,” the scientists note.
As a result, 74% of delta infections occurred in the pre-symptom stage – more than with previous strains. This high figure helps explain how this option became dominant around the world.