As concerns over the novel coronavirus spread across the United States with the pandemic, unfortunately an old face has reared its ugly head: xenophobia.

Before widespread physical distancing measures shuttered many restaurants, for example, Houston’s Chinatown businesses experienced a radical drop in customers because of associations of the coronavirus with the Chinese population, something President Trump has encouraged in his tweets and speeches. Even after the president stressed that the spread of the virus was not the fault of Asian Americans and said he would stop using the “Chinese” label for the virus, his administration reportedly made a similar label a condition for an international agreement with the G-7 countries. It’s clear that the administration has used the pandemic to foster a sense that foreign-born people threaten this nation — rather than working to slow the spread of the illness within it.

This turn toward medical xenophobia and the effort to articulate racial differences with the language of disease is not new, and it has dangerous ramifications. By framing groups of people as inherently unhealthy and vectors for disease, officials in the 19th century Texas borderlands justified intrusive, harmful treatment of Mexican and Mexican American people as a medical necessity. They then used this to intensify beliefs of white supremacy and construct racially driven stereotypes of unhealthy Mexicans. By echoing this practice today with border closures and casting the coronavirus as a foreign threat, the Trump administration is exacerbating the crisis and undermining best public health practices. The result could be deadly, not only for targeted groups, but for all of us.

From the moment the United States arrived in South Texas, Anglo-Americans cast Mexican people as medically suspect. After the U.S.-Mexico War, the Treaty of Guadalupe Hidalgo ceded the northern half of Mexico to the United States in 1848. Anglo-Americans worked to incorporate the Rio Grande Valley into the nation and build white American settlements at the outer limits.

Successful new settlements hinged on health. At this time, before scientists identified germs as sources of disease, people believed a healthy environment, defined by a range of markers, made individual bodies healthy. In 1848, for example, Massachusetts-native Helen Chapman moved to Brownsville, Tex., with her husband, Lt. William Warren Chapman, and she wrote glowing letters to her mother about the medical effects of the Texas climate. “I am in almost robust health,” Chapman wrote. “The extreme dryness of this summer climate and unvarying temperature affects me most favorably.” Likewise, Surgeon S.P. Moore, a military doctor, found Brownsville “decidedly healthy,” and he basked in the “delightful Gulf breeze from the east every morning during the summer, which is the harbinger of health.”

Along with environments, Anglo settlers and physicians also believed that morality made people healthy. They promoted certain qualities — hard work, cleanliness and temperance — that allegedly helped individuals acclimate to new environments. The problem? This medical idea reflected dominant cultural ideas of proper behaviors associated with the 19th-century white middle class. So if a person didn’t display these behaviors, especially in a multiracial place like Texas, they could be cast as unhealthy.

Working to build healthy, moral societies in the Lone Star State, Anglos viewed their Mexican neighbors as culturally and morally defective and saw them as dirty, promiscuous and therefore unhealthy. In another letter, Helen Chapman wrote, “They are a strange people, these Mexicans, good hewers of wood and drawers of water, but low on motive power.” Anglos interpreted Mexicans’ so-called laziness medically, which implied that the entire population was inherently unhealthy.

These ideas gave birth to the image of the “dirty Mexican,” an enduring U.S. racial trope. Moore emphasized the uncleanliness of Mexican neighborhoods in Brownsville, writing, “The Mexicans are a miserable race of beings … existing in squalid wretchedness in their foul cabins, very ignorant and superstitious.” This depiction came a few years after the 1849 cholera epidemic struck the area. There were structural reasons the disease spread through Mexican neighborhoods, as poor, dense living conditions facilitated cholera’s transmission. However, Moore ignored this, making racial arguments instead that reinforced perceptions of ethnic Mexicans as racially inferior to whites.

Race then became justification for medical action. In the 1880s, for example, the U.S. Marine Hospital Service responded to a yellow fever epidemic by quarantining predominantly Mexican towns in South Texas and cutting them off from the rest of the state. Doctors didn’t know the mosquitoes transmitted the disease. So quarantining didn’t work. In fact, it exacerbated a sense that public health initiatives didn’t work to protect Anglos, which intensified discrimination. In Dr. Moore’s description of Brownsville and its population decades earlier, he underscored the medical dangers that these Mexican spaces and Mexican peoples posed to Anglo Americans, an idea continuously applied in Texas.

Even though Mexicans had lived in Texas for generations, Anglos came to see all Mexicans as foreign as a result of these medical-racial assumptions, which then became justification for imperialism and violent treatment at the hands of Anglo Americans. The same scripts repeated later in the 19th century and into the 20th, as Anglos continued to frame Mexican people as a threat to American health, at border crossings and during epidemics. The United States then used this approach at ports of entry for foreign-born people more broadly. Immigration officials conducted intrusive and humiliating exams among entire groups of people that it marked as disease carriers. On Angel Island in California, and at the U.S.-Mexico border, for example, U.S. authorities stripped Chinese and Mexican immigrants naked to examine their bodies, applied toxic sprays and sent them to kerosene baths.

As we grapple with covid-19 and, later, assess our responses, we should resist the president’s insistence that the pandemic we face is a foreign import. By casting the disease as foreign, the administration has sought to avoid responsibility for dealing with all of the homegrown problems that make containing the spread of the illness so difficult: our poor health care system, our lack of social safety net and the administration’s own failure to provide testing. Two centuries ago Anglo-Americans invented the idea of the “foreign virus” to package as scientific the violent expansion of the nation for white Americans. We can’t let this happen again.