A vector transferred the infected agent from the animals which are infected to the human, which results in vector-borne disease.
Mosquitoes are one of the examples of the biological vector which causes vector-borne diseases by carrying an infectious agent they transfer to the human through its bite.
Disease which is transmitted by the mosquitoes is dengue, yellow fever, malaria, etc.
Thus this how mosquitoes can transmit viruses from one organisum to another by acting as biological vector which carry infectious agent.
Since the dog watches her leave and is sad realized that her grabbing the cat keys signals that she is leaving because it is one of the last things she does before she leaves
