Interestingly, seronegative subjects highly exposed to the virus, either because of their close and daily living with infected relatives or because of their health work with COVID-19 patients, have significantly higher ACE2 levels than those who are seropositive with similar exposure conditions (p< 0.0001 in both cases, two-tailed Mann-Whitney test, as for the other indicated p-values unless otherwise stated). Here, ACE2 is linked to COVID-19.