With the fast-growing public transportation infrastructure and increasing socioeconomic activities, travel has become an important issue in the prevention of emerging airborne infectious diseases such as influenza, especially during the introduction period. Obviously, the presence of airports and high densities of transportation routes coincide with more developed areas (i.e., those with a higher population density and more medical facilities); however, after we corrected for these factors, proximity to airports and the presence of national highways or freeways remained significantly associated with the spread of the infection.