Sheriff deputies will begin stopping buses headed to Port Authority from viral U.S. hotspots as part of New York City's continued effort to stem any travel-related upticks in virus cases, Mayor Bill de Blasio said Tuesday. They'll give riders contact forms to fill out with their information and quarantine plans. It's the latest measure the mayor has introduced to help enforce the tri-state quarantine order, which requires travelers from U.S. places with high viral rates to self-isolate for 14 days upon entering New York, New Jersey and Connecticut. In recent weeks, de Blasio has authorized random vehicular checkpoints and ordered hotels to deny travelers room access if they refuse to fill out the form. De Blasio has said up to 20 percent of New York City's COVID-19 cases have stemmed from out-of-state travel. Travelers who land at New York airports from one of the hotspots must also fill out a form or potentially face a $2,000 fine.