In another study on human coronaviruses (HCoV) in CF children, researchers did not find a significant association of HCoV infections with pulmonary exacerbations; however, those infected by HCoV-NL63, which also uses ACE2 for cell entry, had a significantly higher rate of pulmonary exacerbation than those with other coronavirus infections [43]. Here, ACE2 is linked to cystic fibrosis.