Why does the delta variant spread so fast?

The delta variant spreads much faster than other Covid-19 strains—and scientists may now know why. People infected with the delta variant have more than 1,000 times the viral load—the concentration of viral particles in the body—than those with the original strain found in China, a group of scientists has reported in a preprint paper. Scientists at China’s Guangdong Provincial Center for Disease Control and Prevention found, traced, and isolated 62 cases of the delta variant and conducted daily RT-PCR tests on those infected.