Ключевые слова: biohazard, biological, blackboard, board, chalk, chalkboard, class, classroom, cocronavirus, college, communication, contagion, coronavirus, danger, dangerous, disease, education, epidemic, flu, health, infection, infectious, isolated, isolation, letter, medical, medicine, message, outbreak, pandemic, prevent, prevention, protection, protective, quarantine, quarantined, school, segregation, separation, sick, sign, stamp, symbol, temperature, text, virus, warning, wooden,