State one difference between contagious diseases and non-contagious diseases.

Explanation

**Step-by-Step Text Solution:**

1. **Definition of Contagious Diseases**: Contagious diseases are illnesses that can be transmitted directly from one person to another through physical contact or through the air. For example, if a person with a contagious disease like the common cold coughs or sneezes, the virus can spread to others nearby.

2. **Definition of Non-Contagious Diseases**: Non-contagious diseases, on the other hand, are not spread through direct contact between individuals. Instead, they may require a specific agent (like a vector or environmental factor) to transmit the disease. An example of a non-contagious disease is dengue fever, which is transmitted by the bite of an infected Aedes mosquito.

3. **Key Difference**: The key difference between contagious and non-contagious diseases lies in their mode of transmission. Contagious diseases spread through direct contact between individuals, while non-contagious diseases require an intermediary agent (like a vector) for transmission.

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