Countries around the world began issuing various travel restrictions affecting multiple countries in southern Africa Friday, in response to a new variant of COVID-19 that was detected earlier this week. B.1.1.529, now known as the Omicron variant, was first detected by scientists in South Africa, and has also been found in Botswana and Hong Kong in travelers from South Africa. Israel announced it has detected the country’s first case on Friday, and Belgium has become the first European Union Country to detect a case.

“There are fewer than 100 full genome sequences that are available. We don’t know very much about this yet,” WHO COVID-19 technical lead Maria Van Kerkhove said Thursday. “What we do know is that this variant has a large number of mutations, and the concern is that when you have so many mutations, it can have an impact on how the virus behaves.” Despite these concerns, the WHO warned against any “knee-jerk responses” to the new COVID-19 variant.

“We’ve seen in the past, the minute there’s any kind of mention of any kind of variation and everyone is closing borders and restricting travel,” WHO head of emergencies Dr. Michael Ryan said. “It’s really important that we remain open, and stay focused.”

That warning appears to have fallen on deaf ears. As of Friday, the following countries have taken the following steps in response to the new COVID-19 variant:

• The United States will restrict travel from South Africa and seven other countries in the region beginning Monday.
• The EU moved towards stopping air travel from southern Africa.
• The United Kingdom banned flights from South Africa, Namibia, Lesotho, Eswatini, Zimbabwe and Botswana.
• Flights from South Africa to Germany will only be able to transport German citizens home, and travelers will need to go into quarantine for 14 days whether they are vaccinated or not.
• Italy banned entry to anyone who has been in South Africa, Lesotho, Botswana, Zimbabwe, Mozambique, Namibia and Eswatini in the past 14 days (the Netherlands and the Czech Republic are planning similar measures).
• Japanese nationals traveling from Eswatini, Zimbabwe, Namibia, Botswana, South Africa and Lesotho will have to quarantine at government-dedicated accommodation for 10 days and do a COVID test on Day 3, Day 6 and Day 10.

“The early indications we have of this variant is that it may be more transmissible than the delta variant, and the vaccines that we currently have may be less effective against it,” U.K. Health Secretary Sajid Javid said Thursday.

The news of the Omicron variant and the ensuing travel restrictions caused stocks to sink on Wall Street Friday. The Dow Jones Industrial Average briefly fell more than 1,000 points, and the S&P 500 index had it’s worst day since February, dropping 106.84 points.

The price of oil fell about 13% amid worries of another slowdown in the global economy due to the new COVID-19 variant. That’s the biggest decline since the early part of the pandemic. Exxon shares fell 3.5% while Chevron fell 2.3%.