Why SARS-CoV-2 replicates better in the upper respiratory tract

Researchers have assessed virus growth and activation of the cellular defense mechanisms in the respiratory tract. They have shown that natural temperature differences that exist in the upper and lower respiratory tract have a profound influence on SARS-CoV-2 replication and subsequent innate immune activation in human cells. The findings can help to develop antiviral drugs and preventive measures.

source https://www.sciencedaily.com/releases/2021/03/210331114747.htm