COVID-19 can infect people of any age, but individuals with pre-existing medical conditions and older individuals are more susceptible to the virus. This means that while anyone can contract COVID-19, those who have underlying health issues or are in the older age group are at a higher risk of developing severe symptoms or complications from the disease. The answer emphasizes that susceptibility to COVID-19 is not limited to a specific age group or gender, but certain factors can increase the likelihood of severe illness.