It could come down to a nose, or more accurately, the age of a nose, when it comes to unpicking why children seem less vulnerable to infection with SARS-CoV-2.  

US researchers believe their findings on angiotensin converting enzyme 2 (ACE2) receptors in nasal passages may provide a clue for the different ways the coronavirus behaves in children and older adults.  

Children account for less than 2% of identified cases of COVID-19, note the authors, of the Icahn School of Medicine at Mt Sinai in New York. 

One hypothesis is that the lower risk among children is due to differential expression of ACE2, the receptor that SARS-CoV-2 uses for host entry, which varies with age.