Viruses

Viruses are much smaller than cells. In fact, viruses are just capsules that hold genetic material. To reproduce, viruses invade cells in the body. They take over the process that makes cells work. In time, host cells often are destroyed during this process.

Viruses are responsible for causing many diseases, including:

• Common cold.
• Influenza.
• Measles.
• Chickenpox and shingles.
• Coronavirus disease 2019, also called COVID-19.

Antibiotics kill or block activities bacteria need to live or grow, but antibiotics don't work on viruses. Medicine that treats viral infections is called an antiviral. These medicines usually stop a virus from making copies of itself. They also may stop a virus from going into or leaving a cell.