What is a virus?
A virus is an extremely small particle: it cannot be seen with an ordinary school microscope, only with a powerful electron microscope. It does not grow or multiply outside a living cell; only inside a living cell can it multiply: it forces the cell to make new viruses. A bacterium, by contrast, is a single-celled living thing that lives on its own. When a sick person sneezes or coughs, viruses spread into the air; they can also be on door handles, money and similar objects. So when you come home, wash your hands with soap and do not touch your face, eyes and nose. When sneezing, cover your nose and mouth with your elbow or a tissue. Flu and acute respiratory viral infection (ARVI) are viral illnesses. Antibiotics work against bacteria, not against viruses; do not take medicine a doctor did not prescribe. A vaccine is a harmless introduction of a killed or weakened germ (or a piece of it) that teaches the white blood cells to recognise the illness. Vaccination protects reliably against dangerous diseases such as measles.
“True or false”: the teacher reads rules (for example “eat without washing hands” — false; “sneeze into your elbow” — true). Correct the false rules together.