As Harvey’s devastation raged through Houston recently, the city’s mayor was compelled to address rumors that those seeking aid could be deported.

In the wake of a statewide ban on “sanctuary cities,” the mayor sought to reassure the Houston area’s more than 500,000 undocumented immigrants that they would not be targeted for deportation at emergency shelters.

Nevertheless, out of the disaster have come stories of immigrants afraid to seek shelter, and of undocumented mothers sitting at home with their American-born children, weighing the threat of rising floodwaters against a newly “unleashed” immigration enforcement effort.

The reluctance to access help did not surprise Sandro Galea, the dean of Boston University’s School of Public Health, who spoke with me after the hurricane struck. “Rampant stories of unchecked powers of Immigration and Customs Enforcement agents” have created a “justifiable fear” among immigrant populations, making them too worried to ask for any kind of aid, he said.

I’ve seen the same thing in my primary care clinic in Everett, where the past eight months have seemed like so much rising floodwater, threatening the trust that is so vital to me as a physician.

President Trump’s first executive orders on immigration enforcement were handed down as I was facing the height of flu season. My office was filled with people with fevers, coughs and muscle aches.

Since I speak Spanish and Portuguese, and two out of five Everett residents are foreign born, most of my patients are immigrants. Some are newly arrived, some have been in Everett for 20 years. Nearly all described a heightened sense of anxiety about their family’s place in the country, as rhetoric about immigrants turned increasingly hostile.

The fear and anxiety of my patients was palpable, and affected all aspects of our interactions. Questions about where they lived and what kind of work they did suddenly seemed dangerous. Patients began asking me if their answers would be used against them, and if their medical records could be read by immigration authorities. Many declined routine care, worried that they would be targeted by immigration authorities.

And now, more bad news has come, as the administration has announced plans to end a temporary hold on deportations of immigrants who entered the country illegally as children. I dread seeing my young patients who have built lives, businesses and military careers under this program. How will I convince them to push forward, to stay healthy and keep dreaming?

One of my patients quit taking her diabetes medications and nearly died of an infection. “It just felt like nothing mattered,” she recently confessed to me, as we counted her unswallowed pills. Meanwhile, many declined the flu vaccine, one of our best tools to stop yearly epidemics.

What must I have looked like to my patients, a white woman in a white coat, offering them an injection they hadn’t ask for, in a country that did not seem to want them?

Across town, a colleague shares the recent story of caring for a woman in the ICU who had stopped coming to the clinic for her diabetes, for fear of being deported. Though she had been in the country for decades, she no longer felt safe. When she got flu symptoms, her family told my colleague, she continued to stay home out of fear. When she finally showed up at the hospital, it was too late. She had a massive heart attack and died. Her family was devastated and angered by their needless loss.

These stories, while important, cannot convey the full impact that increased deportations will have on the health of individuals and our country as a whole. But research on the health effects of statewide immigration policies and local raids can give us some insight into what the consequences may be.

The controversial “show me your papers” law, which was enacted in 2010 in Arizona, required police to verify the status of anyone whom they “suspected” of being in the country illegally. Researcher Russell Toomey and his colleagues found that teen mothers of Mexican heritage, who were already at high risk of poor outcomes, were 7 percent less likely to bring their baby to the doctor after the law was passed. These effects were actually stronger for second-generation citizens, whose own mothers were born in the U.S.

Toomey explained in an interview that, “while the policy is targeted at undocumented immigrants, it has this spillover effect on Latino women” who are citizens or authorized immigrants. He speculated that these laws were perceived as racially discriminatory, creating a sense of mistrust even for Latinos born in the U.S. As a result, similar policies are likely to widen poor health outcomes for all Latinos.

This mirrors more recent research on an immigration raid that took place in a meat-processing plant in Iowa in 2008. Nearly 10 years later, researchers found there was a 24 percent increase in low-birth-weight births for all Latino mothers in the town, regardless of whether they were born in the U.S. or abroad.

These studies raise concerns that increased immigration enforcement could turn Latinos and other immigrant populations into a permanent underclass, disadvantaging even their American-born children from birth.

These policies also put our nation as a whole at risk. They lead Latino populations to seek care in the emergency room instead of the clinic, leading to nearly a billion dollars in preventable hospitalizations.

These policies have also decreased reporting of sexual assault in Los Angeles, leaving others more vulnerable to predators who may act with impunity. This drop in reporting is no surprise to those of us who listen weekly to stories of assault, watching women shake with fear of an assailant but remain unwilling to call police, who they no longer believe will protect them.

Anti-immigrant policies could potentially even help an epidemic take hold. While it has long been a talking point of American anti-immigrant activists that “immigrants spread disease,” Galea, the BU dean, clarifies that immigrants are actually healthier than native born populations when they arrive. But when immigrants are afraid of accessing care, Galea says, their communities can become “reservoirs of disease,” where people may be afraid to get vaccines, like the flu shot, or seek care when they are sick. When people are afraid to ask for help, infectious diseases will spread faster.

This is not inevitable. In Massachusetts this year, we experienced an outbreak of mumps among Latino populations. The Boston Public Health Commission and other local public health entities were able to partner with Latino organizations, like the Chelsea Collaborative, which have long-established relationships in the Latino community, and were able to use these connections to bring affected people into the clinics. As a result, they were able to contain the outbreak and help people access care.

It was also important that Boston had leadership that signaled its support for immigrant communities, according to Julia Gunn, director of the Communicable Disease Control Division at the city public health commission.

“Right now, we have a very strong mayor [in Boston] who is very supportive of social justice in immigrant communities, and this allows us to do our work,” she said in an interview.

Harvey won’t be the last disaster we face as a country. A future crisis could be as mundane as a flu, as exotic as Ebola, or something we cannot yet dream of. In a globalized world, border fences cannot keep out airborne diseases any more than levees can stop a hurricane. Crises will come, and without the faith of those affected, we will not be able to respond effectively.

Elisabeth Poorman is an internal medicine physician.  She can be reached on Twitter @DrPoorman. This article originally appeared in WBUR’s CommonHealth.

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