A wider outbreak could test the principle of open borders that is fundamental to the European Union. Here are the latest updates and maps of where the virus has spread.

In other developments:

President Moon Jae-in put South Korea on high alert, after more than 760 cases of the virus were confirmed there. The move empowers the government to ban visitors from China and take other sweeping measures to contain the outbreak.

Pakistan and Turkey temporarily closed their borders with Iran, which announced a weeklong closing of schools, universities and cultural centers. The outbreak has killed at least 12 people in Iran, according to state television, the largest number of deaths outside China.

Stock markets in Asia and Europe fell today, and futures markets suggested that Wall Street would also open lower.

In the U.S., the search for places to quarantine Americans is running into resistance from local officials who don’t want patients housed in their communities.

Spreading ‘much faster than I expected’

With all of the coronavirus news, it seemed like a good time for a little perspective. We posed some questions to Donald McNeil, a Times reporter who has covered epidemics and pandemics for nearly two decades.

What worries you about this virus?

It’s more deadly than flu, and it’s spreading like flu. Maybe not quite as fast, but these cases where hundreds of people were infected in one church or aboard one cruise ship — that was scary. That was much faster than I expected.

Why are conspiracy theories gaining traction? We’ve reported on the belief in unfounded claims about the origins of the virus: Some say it came from a lab in Wuhan, while Russian actors have spread a theory alleging the U.S. is behind the outbreak.