“African-Americans in Guangzhou are collateral damage of a policy implemented to target Africans, in which Chinese don’t check your visa, just the color of your skin,” said Yaqiu Wang, a China researcher at Human Rights Watch.

“In a bigger context, the Chinese perceive Africans doing business in China as ripping off the state, not paying taxes and overstaying their visas.”

Gordon Mathews, the chairman of the anthropology department at the Chinese University of Hong Kong, and a co-author of “The World in Guangzhou: Africans and Other Foreigners in South China’s Global Marketplace,” was less forceful.

Guangzhou officials at first denied any discrimination.

Last month, an African-American teacher in Guangzhou, who spoke on the condition of anonymity for fear of retribution, was confined for 14 days to a locked hospital isolation room, despite repeatedly testing negative for the virus.