NEW YORK, United States (AFP) — New York — once the worst coronavirus hotspot in the United States — added four states to its travel blacklist Tuesday, meaning those residents must quarantine for 14 days on arrival.

The full list now stands at 22, with the addition of Minnesota, New Mexico, Ohio and Wisconsin, Governor Andrew Cuomo announced in a statement.

Delaware has been removed from the list.

The number of states on the list has nearly tripled in about three weeks — a sign of the resurgence in virus cases in several parts of the country, especially the Sun Belt.

States are targeted based on an average rolling positivity rate of 10 percent or higher, meaning 10 percent of those tested are positive for COVID-19.

The list includes Florida, California and Texas — the nation’s three most populous states where the number of cases has exploded. New York is fourth in terms of population.

Until now, there has been no formal quarantine control operation.

But from Tuesday, enforcement teams will be stationed at the state’s airports to ensure that arriving travellers complete a state health questionnaire that includes their contact information.

The United States is by far the country hardest hit by the global pandemic, with nearly 3.4 million cases and more than 135,000 deaths.