The U.S. is enacting travel bans in an effort to limit the spread of the new omicron variant of the coronavirus, which the World Health Organization warns poses a "very high" global risk.

Starting Monday, President Biden has imposed travel restrictions for non-U.S. citizens from the following eight countries:

The European Union, Canada, United Kingdom, and Israel have announced travel restrictions from southern African countries as well.

Some health officials and public health experts caution that travel restrictions alone may not be effective in controlling the spread of infectious disease, and could even have harmful effects, like exacerbating xenophobia and deterring countries from being transparent about the state of the virus in the future.

The variant was first reported last week in South Africa, where vaccination rates are about 24%.

Cases of the omicron variant have since been confirmed in Botswana, the United Kingdom, Italy, Germany, Belgium, Israel, the Netherlands, Australia and Hong Kong.

Biden is encouraging children and adults to get vaccinated against COVID-19.

"This pandemic will not end until we have global vaccinations," he said last week in a statement.

In an address on Monday, he said the variant is "a cause for concern — not a cause for panic."

Tien Le is an intern on NPR's News Desk.

This story originally appeared on the Morning Edition live blog.

Copyright 2021 NPR. To see more, visit https://www.npr.org.