**Core Concept**
Q fever is a zoonotic disease caused by the bacterium Coxiella burnetii. It is primarily transmitted through inhalation of infected dust particles or aerosols that contain the bacteria. This mode of transmission is a result of the bacteria's ability to survive in a dormant state outside of a host.

**Why the Correct Answer is Right**
The bacteria Coxiella burnetii can infect a wide range of animals, including livestock and rodents. When an infected animal excretes the bacteria, it can be aerosolized into the air and become airborne. Humans can then inhale these infected particles and become infected with Q fever. This process is known as inhalation of infected aerosols.

**Why Each Wrong Option is Incorrect**
- **Option A:** Q fever is not primarily transmitted through direct contact with an infected animal. While direct contact may occur, the primary mode of transmission is through inhalation of infected aerosols.
- **Option B:** Q fever is not transmitted through a vector like a tick or mosquito. While ticks and mosquitoes can transmit other diseases, Coxiella burnetii is primarily transmitted through aerosols.
- **Option C:** Q fever is not transmitted through contaminated food or water. While the bacteria can be present in contaminated food or water, the primary mode of transmission is through inhalation of infected aerosols.

**Clinical Pearl / High-Yield Fact**
Q fever is often referred to as "the great imitator" due to its nonspecific symptoms, which can mimic those of other diseases such as pneumonia, hepatitis, or endocarditis. This makes it challenging to diagnose, and a high index of suspicion is necessary.

**Correct Answer: D. Inhalation of infected aerosols.