When the COVID public health emergency ends on May 11, laboratories across the United States will no longer be required to report coronavirus test results to the Centers for Disease Control and Prevention. Hospitals and state health departments, too, will report less comprehensive data, making it more difficult for the federal agency responsible for detecting and responding to public health threats to protect Americans.

The winding down of the Biden administration’s coronavirus response and accompanying changes to reporting requirements highlight long-standing vulnerabilities of a fractured public health surveillance system, one that fails to provide reliable information in disease outbreaks – even as experts warn of the potential for the coronavirus to come roaring back.

“What we have right now is not a national public health system,” said Nirav Shah, the CDC’s principal deputy director. “We have a patchwork. And as a result of that, when we want to get data and synthesize it, it takes a lot of legwork that takes way too long.”

Shah is the former head of the Maine Center for Disease Control.

The coronavirus pandemic showed how critical real-time public health surveillance is for a basic understanding of outbreaks, such as how many people are sick or dying, whether a situation is getting better or worse, and which demographic groups are hardest hit, said Tom Inglesby, director of the Johns Hopkins Center for Health Security, who co-wrote a report on how to improve the CDC’s operations and pandemic response.

Public health officials have been hamstrung in their ability to control the spread of infectious diseases, from pox to measles, given the inconsistent and fragmented way data is reported from hospitals, doctor’s offices, and laboratories to local and state authorities and ultimately, the CDC.

During the mpox outbreak last year, CDC Director Rochelle Walensky said the agency was responding “with blind spots in our data on how and where the disease was spreading … limited by our patchwork system of data use agreements with states and jurisdictions.” Even though federal officials outlined a national mpox vaccination strategy in June, it was not until September that the CDC had established agreements with individual states to get information on who was getting vaccinated, Walensky said at a recent public health forum hosted by KFF, a health policy nonprofit.

It’s up to states to decide what kind of data and how often to report to the CDC. There is no central repository for collecting the information in any sort of consistent or uniform way. Some state health agencies tracking the spread of disease still rely on healthcare facilities to report information to them via fax machines.

“What we saw from COVID is that our systems are very fragile,” said Inglesby, who was in charge of testing as part of the White House COVID-19 response. “In some places, we can’t collect information on demographics so we don’t know which groups are at the highest risk.”

Walensky, who is stepping down on June 30, has repeatedly highlighted the need for Congress to provide additional funding and authority to the agency to strengthen its ability to collect data. To stop disease outbreaks, the agency must have a “line of sight” as to when those infectious threats are sparked, Walensky said during last week’s Senate hearing about pandemic preparedness.

The agency has requested $340 million in next year’s budget for its data modernization efforts, but experts say the program’s existing funding is at risk as Republicans seek to pull back unspent coronavirus funds as part of ongoing debt ceiling talks in Congress and as the pandemic slips further from public concern.

CDC officials say the coronavirus remains a priority, but its surveillance will be folded into a wider strategy for monitoring respiratory viruses. The agency will no longer track community levels of COVID-19 or transmission rates after May 11. Instead, the CDC will rely on a variety of other measures, including hospital admissions, emergency room visits, and wastewater surveillance to track COVID-19 trends.

“We will still be able to tell that it’s snowing, even though we’re no longer counting every snowflake,” Shah said.

But states control their responses to emerging infectious diseases, with state laws dictating how health data is collected and shared. Without a health emergency, the CDC has to develop data use agreements for every new disease with each state and territory. In the past weeks and months, the CDC has had to negotiate individually with state and local officials to collect information on who is getting coronavirus vaccines.

South Carolina, for example, will no longer send daily updates on the age, sex, and race of people who have received a coronavirus vaccine to the CDC because state law does not allow sharing of data – to any entity – except in about a dozen circumstances, including a public health emergency, said Brannon Traxler, director of public health for South Carolina’s department of health and environmental control. After May 11, the state will continue to track the coronavirus and COVID-19 vaccinations in detail internally, she said, but only certain information will be posted on its public dashboard.

The bigger issue going forward is that most states do not require health facilities to report adult immunizations, said Janet Hamilton, executive director of the Council of State and Territorial Epidemiologists. As soon as the federal supply of coronavirus vaccine ends, and the vaccine is commercialized and distributed by the private sector, most states won’t know how many adults are getting coronavirus vaccines and therefore, won’t know who is most at risk for severe infections.

Before the pandemic, only 187 healthcare facilities were equipped to report disease cases electronically to state health departments. That number has since grown to about 25,000 facilities, but that’s still only about 20 percent of all healthcare facilities in the United States, according to Walensky.

During the pandemic, the CDC received COVID data from 64 states and territories, 3,000 counties, and 574 tribes, “and they all come in different ways, different times, different systems, different standardizations,” Walenksy said at the KFF forum.

“That is not an acceptable data system. It improved during the public health emergency for COVID,” she said. But “what happens when we have to do this for, name your next, you know, scary pathogen?”

As public attention to the pandemic fades, officials and experts worry that any urgency to fix systemic issues will disappear.

“The vulnerabilities that were exposed during COVID will continue after unless action is taken,” said David Fleming, an epidemiology professor at the University of Washington School of Public Health, who was a former deputy director of the CDC as well as former Oregon state epidemiologist and former director of the Seattle-King County health department.