On the other hand, studies have shown that COVID‐19 patients have a lower concentration of ACE2 monocyte expression—the endogenous entry receptor of SARS‐CoV‐2—and researchers hypothesize that the virus can remain dormant in peripheral blood mononuclear cells and cause a relapse after the respiratory system has been cleared of the virus and patient has tested negative.38, 39, 40. Here, ACE2 is linked to COVID-19.