Contagious is “transmissible by direct or indirect contact with an infected person.”
Infectious is “producing or capable of producing infection” and “containing pathogenic agents which may be transmitted.”
Both infectious and contagious diseases are caused by bacteria and viruses;
They differ in that contagious diseases may be spread by direct or indirect contact.
An ailment such as food poisoning is infectious, it is capable of producing infection, but it is not contagious. The coronavirus, on the other hand, is both contagious and infectious.
Anything that is contagious is automatically also infectious, but the reverse is not true.
[출처] www.merriam-webster.com/words-at-play/coronavirus-words-guide/covid-19
