Answer:
The correct answer is the effect of air travel on the occurrence of the flu transmission.
Step-by-step explanation:
The public health experts who examine the causes and patterns of disease and injury in humans is known as an epidemiologist. They help to minimize the incidence and threat of negative health outcomes via research, health policy, and community education. As Greg is an epidemiologist so he will examine the effect of travelling via air on the occurrence of flu transmission.