The C.D.C. is still unprepared to respond quickly to disease threats posed by international travel, a U.S. audit finds.

The U.S. Centers for Disease Control and Prevention’s reliance on outdated systems to collect and analyze data on international air travelers continues to hamper its ability to respond quickly to disease threats, according to a new report by the Government Accountability Office.

The report said that limitations in how the C.D.C. collects and manages contact information for air travelers makes it difficult to conduct contact tracing and track public health risks. The agency, the G.A.O. found, “is unable to quickly and accurately identify the number of passengers exposed to a specific infected passenger on a flight.”

Two and a half years after the coronavirus began to spread across the globe, the G.A.O. said in a statement on Tuesday that the pandemic “highlighted how unprepared the U.S. public health and aviation systems are to respond to public health threats.”

The G.A.O.’s findings carry a sense of urgency this summer, as tourism and travel have begun to approach prepandemic levels even though the BA.5 subvariant of Omicron is fueling a surge in cases in many countries.

In the United States, reported cases are averaging more than 100,000 a day — a figure that is likely to be undercounted given an increasing reliance on at-home testing and the closures of mass testing sites.

The C.D.C. did not immediately respond to a request for comment on Tuesday. The G.A.O. did note some changes the agency had made, but said its data systems still needed “substantial improvement.” It said that the C.D.C. had “concurred with the recommendations” in its report, including that the agency redesign its data system or develop a new one.

U.S. authorities have made efforts to trace travelers who may have contracted Covid-19 abroad. For example, in late November, when Omicron cases were rising in southern Africa, officials directed airlines to share contact information for passengers who flew from the region into the United States.

The C.D.C.’s data management system was developed in the mid-2000s, the G.A.O. report said, and “was not designed for rapid assessment or aggregation of public health data across individual cases.” That hobbled the agency, the report said, meaning the C.D.C. “is not positioned to efficiently analyze and disseminate data to inform public health policies and respond to disease threats.”

Concerns have been raised about the global transmission of highly infectious diseases since the SARS epidemic in the early 2000s.

“More than any other mode of transportation, air travel creates the potential for infectious diseases to move quickly from one part of the world to another,” the report said.

The data system used by the C.D.C. prompted contact investigations from about 80 to 130 flights each year from 2015 to 2019, and about 25,000 flights in 2020, according to the report.