Children of all ages are more perceptive than adults tend to think. Even if you have not spoken to your child about COVID-19, your child almost certainly is aware that something big is happening (and probably knows more than that).
When you feel calm, and are familiar with the facts, you should have an informed, direct, and developmentally appropriate conversation with your child. You know better than anyone what your child has seen, experienced, and understands about concepts like getting sick and how diseases spread, so tailor your discussion accordingly.
The good news is that the science supports your being appropriately reassuring about their risk. Children CAN get sick, but they might be asymptomatic and are unlikely suffer severe symptoms. You might explain that older people are at risk of getting sick, and that we all need to work together to protect them.
In general, children like to be helpful to others. Talk to your child about how good hygiene, staying home, and not visiting at-risk adults will help keep others from getting sick.
Finally, keep the conversation going: revisit the topic regularly with new information and remember to praise your child for the things they’ve done to be safe and helpful.
Here are some helpful resources: