Photo: Spencer Platt/Getty Images

Visitors from eight additional states will be required to quarantine for 14 days when traveling to New York, New Jersey and Connecticut, bringing the total number of states subject to the tri-state area's restrictions to 16.

Why it matters: The tri-state area, the original hub of the coronavirus outbreak in the U.S., has successfully flattened its curve and is beginning to reopen. Officials fear, however, that the surge of cases in others states across the country will erase New York and its neighboring states' progress.

The big picture: "The quarantine applies to any person arriving from a state with a positive test rate higher than 10 per 100,000 residents over a 7-day rolling average or a state with a 10% or higher positivity rate over a 7-day rolling average," Gov. Andrew Cuomo said in a press release.

Full list (***new states)

  1. Alabama
  2. Arkansas
  3. Arizona
  4. California***
  5. Florida
  6. Georgia***
  7. Iowa***
  8. Idaho***
  9. Louisiana***
  10. Mississippi***
  11. North Carolina
  12. Nevada***
  13. South Carolina
  14. Tennessee***
  15. Texas
  16. Utah

Go deeper: New Jersey pauses reopening process as coronavirus cases surge in other states

Editor's note: This story has been updated to note that New Jersey and Connecticut will also require travelers from these states to quarantine, in addition to New York.

Go deeper

Coronavirus cases flat or growing in 48 states

Data: The COVID Tracking Project, state health departments; Map: Andrew Witherspoon, Sara Wise, Naema Ahmed, Danielle Alberti/Axios

The number of coronavirus cases increased in the vast majority of states over the last week, and decreased in only two states plus the District of Columbia.

Why it matters: This is a grim reminder that no part of the United States is safe from the virus. If states fail to contain their outbreaks, they could soon face exponential spread and overwhelmed health systems.

Case growth outpacing testing in coronavirus hotspots

Data: The COVID Tracking Project. Note: Vermont and Hawaii were not included because they have fewer than 20 cases per day. Chart: Andrew Witherspoon/Axios

The United States' alarming rise in coronavirus cases isn't due to increased testing — particularly not where cases have grown fastest over the last month.

Why it matters: The U.S. doesn't yet know what it looks like when a pandemic rages on relatively unchecked after the health system has become overwhelmed. It may be about to find out.

Updated 19 hours ago - Health

Which states have set single-day coronavirus records in the past week

Data: Compiled from state health departments by Axios; Map: Danielle Alberti/Axios

California recorded 11,529 new novel coronavirus cases on Sunday, beating the record it set last week (9,480).

The big picture: At least 15 states have broken their single-day coronavirus infection records in the past week, according to state health department data reviewed by Axios.