A new disease has suddenly appeared, and scientists are trying to determine whether the disease agent is a virus or a bacterium. They collect the following information:
1. The disease can be transmitted through the air.
2. The disease agent is too small to be seen under a compound microscope.
3. There are no known antibiotics that are effective against the disease.
4. The genetic material of the disease agent is DNA.
5. The disease agent cannot be cultured using any known culture medium.
Is the disease agent most likely a bacterium or a virus? Explain your answer.