Which two common diseases do viruses cause?

Explanation

**Step-by-Step Solution:**

1. **Understanding Viruses**: Viruses are microorganisms that are not visible to the naked eye and require a host's body to replicate. They do not have the machinery to divide on their own.

2. **Identifying Common Diseases**: We need to identify two common diseases caused by viruses.

3. **First Disease - Common Cold**: One of the most common diseases caused by a virus is the common cold. It is caused by various types of viruses, primarily rhinoviruses.

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