Federal datasets began disappearing from public view on January 31, 2025, in response to executive orders from President Donald Trump. Among those were the Centres for Disease Control and Prevention’s Youth Risk Behaviour Survey, which asks respondents about their gender identity and sexual orientation and tracks behaviours like smoking and drug use; CDC’s HIV dataset; and CDC and Agency for Toxic Substances and Disease registry’s Environmental Justice Index, which tracks pollution in communities, and Social Vulnerability Index, which identifies communities at high risk for disease and disability.

The collection of public health surveillance data has never been politically neutral. It has always reflected ideas about individual rights. With our colleagues James Colgrove and Daniel Wolfe, we have written about the history and ethics of surveillance. Despite controversy, it remains public health’s foundational tool.

Surveillance typically involves tracking individuals with diseases by name for the purpose of direct action, including isolation, quarantine and treatment. It allows health officials to identify environmental threats and evaluate treatments. It allows governments to direct prevention and treatment resources where they are needed most, be that to a region or a group at highest risk. By the early 20th century, public health officials argued that without surveillance, they worked “in the darkness of ignorance” and “might as well hunt birds by shooting into every green bush.”

Three major controversies in the history of public health underscore what is at stake with the collection and maintenance of this information.

TB and doctors

The collection of tuberculosis data provided the basic blueprint for public health surveillance. Debates over tuberculosis reporting began in the late 19th century, when the bacterial infection was reframed not as a disease of the elite but of the urban poor. New York City was the first in the country to require that physicians report the names of TB patients in an effort to address the leading cause of death in both the city and the US. The medical community bitterly resisted tuberculosis surveillance. A prominent New York City surgeon argued that surveillance represented a “dictatorial … encroachment” of the health department that threatened to rob physicians of their patients.

But most people were not under the care of a private physician, and tuberculosis surveillance was a way to ensure that the largely immigrant poor living in the tenement districts got referrals to clinics, nourishment and, if necessary, isolation. Despite physicians’ attempts to kill these efforts, there was no public outcry about tracking “the great white plague” despite extensive, sensational coverage of the controversy in the popular press.

HIV/AIDS and patients’ resistance

Debates around TB surveillance unfolded during a period in which both public health and medicine were highly paternalistic and authoritarian: Health department physicians or private physicians made medical decisions, not patients. That changed with the AIDS epidemic, the first major infectious disease threat in more than a generation. AIDS arrived as American politics took a sharp conservative turn with the election of President Ronald Reagan. When in 1985 it became possible to test for HIV, the virus that causes AIDS, the prospect of named surveillance triggered deep fears about stigma and discrimination.

The prospect of reporting the names of those with HIV prompted one gay activist to declare, “First comes the national registry, then come the boxcars, then come the camps for people with AIDS.” Gay rights advocates, who prioritised privacy, rejected HIV surveillance as a threat. An alliance of gay rights leaders and civil liberties advocates was initially able to prevent health departments from undertaking named HIV surveillance. But by the end of the 1980s, there was growing pressure to return HIV/AIDS to “the medical mainstream,” meaning that it could be managed therapeutically like other chronic conditions. As effective treatment became available in the 1990s, opposition faded, and all 50 states required named reporting.

Cancer and counting demands

If TB and HIV/AIDS reporting began as histories of resistance, the story was very different when it came to cancer reporting, which lagged far behind infectious disease surveillance. In the wake of the environmental and women’s movements, citizen activists, mothers of children with birth defects and women with breast cancer became alarmed about the threat of cancer linked to pesticides or industrial pollutants. Women with cancer asserted a “right to be counted.” Although the National Cancer Act of 1971 directed the National Cancer Institute to “collect, analyze, and disseminate all data useful in the prevention, diagnosis, and treatment of cancer,” by the 1980s, 10 states still had no registry.

Vermont’s Bernie Sanders, then an independent member of the US House of Representatives, called for a federally funded program to collect data on cancer in every state. Speaking in support of his bill in 1992, Sanders repeatedly invoked communities’ right to know: “We need to know the age of people who are coming down with cancer. We need to know where they live. We need to know the kind of work they do. We need their racial and ethnic backgrounds.” President George H.W. Bush signed the Cancer Registries Amendment Act, which mandated cancer surveillance, into law in 1992. But it was not until 2000 that all states established cancer registries.

Surveillance: foundational for public health

In the broader history of surveillance, two key lessons have emerged. First, despite some pitched battles, communities have more often viewed surveillance as serving their interests. Second, the system of public health surveillance in the US remains an underfunded patchwork. The Pew Environmental Health Commission called birth defects surveillance “woefully inadequate.” In 1972, the US House Committee on Government Operations described occupational disease surveillance as “70 years behind infectious disease surveillance and counting.” In 2010, we ourselves observed that it was now “a century behind and counting.”

The scope of the changes that the Trump administration has planned for federal data systems and datasets is unclear. Per a federal court order, key public health surveillance systems and datasets are back online. But the landing pages for both the Social Vulnerability Index and the Youth Risk Behaviour Survey display a caveat based in politics rather than science that “any information on this page promoting gender ideology is extremely inaccurate and disconnected from the immutable biological reality that there are two sexes, male and female.”

Systems can be compromised if datasets are scrubbed of key variables that enable public health action with populations at highest risk, are halted, or are removed from the public eye. Communities cannot act on what they cannot count.

Fairchild is a professor of sociology at Syracuse University, US.

Bayer is a professor emeritus of sociomedical sciences at Columbia University Mailman School of Public Health, US.

— The Conversation