People traveling into New York, New Jersey, or Connecticut from states with high rates of positive COVID-19 tests will be required to quarantine for 14 days. The new restrictions were announced by the governors of those states in a joint press conference today. The new travel advisory goes into effect tonight.

The three states were the first to be hit hard by the pandemic and were the target of similar travel advisories in March when cases in those states skyrocketed. But recently the numbers of new cases in each has declined dramatically, while the numbers of new cases in other parts of the nation have soared.

“We’ve worked very hard to get the viral transmission rate down and we don’t want to see it go up again because people are traveling into the state and bringing it with them,” New York Governor Andrew Cuomo said.

The states targeted by the new advisory will change depending on the percentage of COVID-19 tests in each state that come back positive. In May, the World Health Organization said that one way areas could figure out if it was safe to reopen was by looking at this positivity rate. If a place was doing enough testing, then they could determine that the epidemic was under control when their positivity rate was below 5 percent for 14 days.

Right now, New York, New Jersey, and Connecticut all have positivity rates well under 2 percent, according to Johns Hopkins. The states plan to keep it that way and will ask travelers from other states with a positive test rate of 10 percent over the last seven days to quarantine for 14 days. They’ll apply the same measures to states with “a positive test rate higher than 10 per 100,000 residents over a 7-day rolling average.”

As of midnight tonight, travelers to New York, New Jersey, or Connecticut coming from Alabama, Arkansas, Arizona, Florida, North Carolina, South Carolina, Utah, Texas, and Washington state will all be asked to quarantine for two weeks.

Enforcement of the policy will depend on each state, Cuomo said at the press conference today. In New York, he said, people who do not quarantine voluntarily may be subject to mandatory quarantine. People caught violating quarantine a first time might be subject to a $2,000 fine, people caught a second time could be fined $5,000, and people who violate quarantine and cause “harm” might be subject to a $10,000 fine. It was not immediately clear what kind of harm might result in that fine.