Ключевые слова: bacteria, bacterium, blackboard, board, chalkboard, concept, danger, defense, disease, epidemic, flat, flu, health, heart, immune, immunity, immunodeficient, immunology, immunotherapy, infection, lay, medical, medicine, ncov, nobody, object, pandemic, prevent, prevention, protection, quarantine, safety, shape, shaped, stethoscope, support, system, table, top, view, virology, virus, wooden, word, written,