Long-term exclusion of strict restrictions in some places
     For example, in South Carolina and Florida, the state government has only recently introduced measures such as a "home order" to provide a window period for the spread of the virus. Mobile phone positioning information shows that even in states and cities where travel restrictions were promulgated earlier, people did not immediately reduce travel, and did not take it seriously until the middle and late March. Health experts say that it usually takes two to three weeks for the restrictive measures to be effective. Areas where travel restrictions are loose may not only become new high-risk areas, but may also threaten other areas where epidemic prevention has achieved results.