Ключевые слова: asia, bacteria, biology, bird flu, city closure, cluster, concept, concepts and topics, coronavirus, covid19, dangerous, death, digital generation, disease prevention, fever, illness, immune system, infection, medical and healthcare, medical diagnosis, microbiology, middle east respiratory syndrome, national flag, pandemic, plague, retrovirus, saudi arabia, saudi arabia flag, science, severe acute respiratory syndrome, symptoms, virus, world flag,