The bodies of animals (mammals) human race being mammal. Possess a variety of defensive mechanism. That prevents the invasion of tissues by diseases causing organisms.
These are classified as primary or secondary mechanisms. Primary mechanisms prevent entry of pathogenic organisms into the internal tissues. Secondary mechanisms destroy organisms that manage to enter into the tissue through immunity process.
Primary Mechanism
(i) Mucus secretions: The respiratory track trap inhaled microbes and propelled upward by cilia cells (muscles) to the pharynx from where they are coughed out. That why covid-19 patients cough.
(ii) Reflex actions : Coughing , sneezing, diarrhea and vomiting are reflex actions that removes foreign materials from the respiratory and digestive tracts when the corona virus has managed to enter and replicated in large numbers, the body inject them through coughing.