The Korea National Institute of Health (KNIH) said it has found reasons smoking, stroke, and diabetes lead Covid-19 patients to develop severe symptoms than others.

A research team of KNIH observed that the angiotensin-converting enzyme 2 (ACE2), which is known as a receptor for the Covid-19 virus to infiltrate into human cells in the lungs, heart, and arteries, increase in smokers and stroke or diabetes patients.

ACE2 reduces blood pressure by transforming the vasoconstrictor angiotensin 2 to the vasodilator angiotensin 1-7.

The Covid-19 virus binds spike protein to ACE2 and penetrates and amplifies cells, causing patients with a lot of ACE2 to be more vulnerable than those who do not have.

The number of ACE2 decreases while the Covid-19 virus penetrates cells. This leads patients to develop severe illness by raising blood pressure with increased angiotensin 2.

The World Health Organization has defined risk factors associated with morbidity or death due to severe conditions caused by Covid-19 as the elderly, chronic diseases, and smoking. Chronic diseases include diabetes, hypertension, immunosuppression, cancers, and cardiovascular, cerebrovascular, chronic respiratory, and kidney diseases.

“The study results imply that smokers and patients with diabetes or stroke have a higher risk of developing severe Covid-19 symptoms due to increased ACE2 in cells,” KNIH Director Kwon Jun-wook said.