**Core Concept**
Measles is a highly contagious viral illness caused by the measles virus, primarily affecting children worldwide. The virus spreads through respiratory droplets, leading to a characteristic rash, fever, and cough.

**Why the Correct Answer is Right**
The measles virus infects the respiratory tract, replicates in the epithelial cells, and then spreads to the lymphoid tissues, triggering an immune response. This leads to a prodromal phase characterized by fever, cough, and conjunctivitis, followed by a rash that starts on the face and spreads to the rest of the body. The virus is highly contagious, with a basic reproduction number (R0) of approximately 12-18, making it a significant public health concern.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because measles is not primarily spread through contact with contaminated surfaces.
**Option B:** Incorrect because the measles rash typically starts on the face and spreads to the rest of the body, not the opposite.
**Option C:** Incorrect because measles is not a zoonotic disease, meaning it does not primarily affect animals.

**Clinical Pearl / High-Yield Fact**
In a measles outbreak, it is crucial to identify and isolate infected individuals promptly, as the virus can spread rapidly to susceptible populations, such as unvaccinated children or immunocompromised individuals.

**Correct Answer:** D.