Viral load 1,000 times higher in people infected with Delta variant

People infected with the Delta variant of novel coronavirus produce a lot more virus particles than those infected with the original version of coronavirus, thereby making their infection very easy to spread, according to a study.

Researchers at the Guangdong Provincial Center for Disease Control and Prevention in China found that viral load—a measure of the density of viral particles in the body—is roughly 1,000 times higher in people infected with the Delta variant than those infected with the original coronavirus strain, Nature reported.

According to current estimates, the Delta variant could be more than twice as transmissible as the original strain of SARS-CoV-2, the virus causing COVID-19. The variant, which was first identified in India in late 2020, has now become the predominant strain and has spread to at least 111 countries.

The team tracked 62 people who were quarantined after exposure to COVID-19, and tested their viral load every day throughout the course of infection to see how it changed over time. Researchers then compared participants' infection patterns with those of 63 people who contracted the original SARS-CoV-2 strain in 2020.

The findings, posted preprint, showed that the virus was first detectable in people with the Delta variant four days after exposure. On the other hand, the original strain took an average of six days to be present in people. This suggests that Delta replicates much faster, said epidemiologist Jing Lu at China's CDC.