The White House announced today stricter rules for travelers. The news comes just one day after the omicron variant was detected in the United States, in California. A second case was confirmed Thursday in a Minnesota resident who recently returned from a convention in New York City. At least 23 countries have identified omicron cases so far, and that number is expected to rise in the coming days and weeks, the WHO said Wednesday.

International travelers and United States citizens returning from a trip outside the country, will be required to test for COVID-19 within one day of departure regardless of their vaccination status. Previously, vaccinated travelers heading to the U.S. were required to present proof of a negative COVID-19 test 3 days before arrival while only unvaccinated travelers were required to comply with the shortened testing window now in place for everyone. The new requirements will go into effect early next week.

The U.S. started restricting travel from eight African countries this Monday due to the new COVID-19 variant. The new rules apply to travelers from South Africa, Botswana, Zimbabwe, Namibia, Lesotho, Eswatini, Mozambique, and Malawi. U.S. citizens and lawful permanent residents are excluded.