“If China shut the door on exports of core components to make our medicines, within months our pharmacy shelves would become bare and our health care system would cease to function,” said Rosemary Gibson, a senior adviser with the Hastings Center and an author of “China Rx: Exposing the Risks of America’s Dependence on China for Medicine.”

“In the event of a natural disaster or global pandemic, then the United States will wait in line with every other country for essential medicines,” she said.

Some in China have also noted these vulnerabilities. An article posted last week by the state news agency Xinhua argued that the world should thank China, rather than blame it for spreading the virus, saying that if China banned the export of drugs, “the United States would sink into the hell of a novel coronavirus epidemic.”

China does not appear to be explicitly blocking the export of pharmaceuticals, though it has cut off exports of face masks by requiring manufacturers to sell masks straight to the government for distribution, leaving none to send overseas.

Factory closings and transportation restrictions in China have disrupted supply chains for drugs as well. Public health officials are watching to see whether the coronavirus epidemic will lead to more shortages of essential drugs in the United States in the coming weeks.

On Feb. 28, the Food and Drug Administration warned that one drug was already in short supply in the United States because of manufacturing issues, and said it was monitoring about 20 others that rely on China.

Last week, the Indian government ordered its pharmaceutical companies to stop exporting 26 drug and drug ingredients, most of them antibiotics. And South Korea, Germany, India, Taiwan and others have clamped down on exports of masks and other protective gear over worries that their own supplies will fall short.