Answer:
The innate or nonspecific immune system includes two lines of defense in the human body. Non-specific means that it does not act on the specific pathogen. It works equally to keep all types of pathogens such as bacteria, viruses, parasites et cetera out of the body.
The first line of defense includes physical barrier which prevents the entry of pathogens into the body. It includes skin, respiratory tract, gastrointestinal tract, cilia, nasopharynx, eyelashes, and body hairs.
It also includes chemical barriers such as mucus, gastric acid, bile, tears, sweat, and saliva.
The second line of defense includes anti-inflammatory responses, fever, and nonspecific cellular responses such as phagocytes, macrophages, complement system et cetera.
Thus, the virus has to pass physical, chemical, and nonspecific cellular responses of the body in order to infect the body.
