. 2021 Oct 21;2021:6699788. doi: 10.1155/2021/6699788
Copyright © 2021 Xia Wang and Hiroshi Nishiura.
This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Figure 1.
The distribution of travelers.