After a 10-day national holiday shadowed by the outbreak, Chinese markets opened Monday and took a tumble. The Shanghai Composite index closed nearly 8 percent lower on Monday evening, marking its biggest daily drop in more than four years. The economic jitters posed by the spread of the virus extended far beyond China’s borders, too. As my colleagues reported, the battle to contain the coronavirus, which has claimed more than 400 lives, may disrupt global supply chains as airlines halt cargo and passenger flights.

“The concern is not the zombie apocalypse with people dying in the streets. The concern is that a huge chunk of the global economy gets put out of commission as people wait it out,” Patrick Chovanec, managing director at Silvercrest Asset Management in New York, told my colleague David J. Lynch.

China’s National Health Commission reported Monday that there are 20,438 confirmed cases in China, including 15 in Hong Kong, which reported the second fatality outside mainland China on Monday night, and eight in Macao. The self-governing island of Taiwan reported 10 cases. The World Health Organization reported 146 confirmed cases in 23 countries outside China. The WHO declared the crisis an international public health emergency last week, but it has yet to deem its spread a “pandemic.” To meet that criteria, The Washington Post’s Miriam Berger reported, “a new disease generally needs to affect many people across international boundaries, either worldwide or throughout a very wide area.” It may be only a matter of time before public health experts invoke that designation.

As fears rise, people have had their lives disrupted by emergency actions taken by governments. Chinese tourists and other foreign travelers exiting the Chinese mainland are now the targets of entry bans in a growing list of countries. Chinese overseas communities have fallen victim to public hysteria. Discrimination has surged in parts of the world, with anecdotes of schools and businesses from Rome to Tokyo seeking to block East Asian students or customers out of fear of contagion.

In Hong Kong, the crisis has exacerbated long-standing feelings of hostility toward the mainland. On Monday, the local government closed all but three border crossings. Medical workers in Hong Kong, feeling overburdened and low on supplies, went on strike and called on authorities to close all checkpoints with the mainland. Nonetheless, the city’s Beijing-backed leader, Carrie Lam, chided the strikers and their calls for a full shutdown of the border.

“If anyone thinks that by resorting to such extreme measures, the government will be made to do something that is not rational or will harm the public good, they will not get anywhere,” she said.

Chinese authorities, meanwhile, criticized certain responses to the virus. On Monday, officials groused over the U.S. reaction to the outbreak, which included conspicuous comments from Commerce Secretary Wilbur Ross that the virus in China could be a boon for job growth in the United States, as well as a temporary ban on most foreign nationals who have traveled to China in the past two weeks.

Chinese Foreign Ministry spokesman Hua Chunying warned against measures that “could only create and spread fear” and lamented the impulse to adopt a siege mentality. “It is precisely developed countries like the U.S. with strong epidemic prevention capabilities … that have taken the lead in imposing excessive restrictions contrary to WHO recommendations,” Hua said.

Some public health experts concur. “Even if it were feasible to keep coronavirus out through travel bans, these measures can make us less safe,” wrote Jennifer Nuzzo, an epidemiologist at the Johns Hopkins Bloomberg School of Public Health. “Travel bans can penalize countries that report cases, which may in turn reduce countries’ willingness to share information about their outbreaks.”

Nuzzo added in her Washington Post column that the “bans may also interrupt the flow of essential supplies upon which we depend to control the epidemic. China is a large producer of critical medicines and personal protective equipment — it is in our best interest to stay positively engaged with China in responding to this epidemic.”

Of course, China has plenty to answer for in its own handling of the outbreak. As my colleagues reported, the authoritarian state’s opacity, and “a bureaucratic culture that prioritizes political stability over all else,” created an environment that led to the virus spreading faster.

China’s geopolitical clout is also complicating how governments in its orbit, especially in neighboring Southeast Asia, are reckoning with the crisis. “The region now has the largest cluster of coronavirus patients outside China,” noted Hannah Beech of the New York Times. “Some governments there have either played down the threat of the epidemic or openly worried about offending a superpower whose economic heft can propel their economies.”