“It’s $500 versus, literally, $5,000,” said Bob Kocher, a partner at the venture-capital firm Venrock, who has been helping California manage its coronavirus testing effort.

In the early 2010s, the federal government spent billions to encourage doctors to replace fax machines with electronic records. That program, known as the HITECH Act, did not include similar funding for public health departments, to help them automatically digitize faxes and other nonstandard results. Nor did it require hospitals and doctor’s offices to build technology that would automatically send relevant test results to local health officials.

Public health departments, whose budgets have been cut back over the past decade, were unable to finance the digital upgrades themselves.

“The best way I can describe it is to imagine you’re on the information super highway, but you’re traveling with a bus pass,” said Oscar Alleyne, chief program pfficer at the National Association of County and City Health Officials. “Money was invested to get physician practices onto electronic health records. There was no investment to build up a similar technology to tie public health into that system.”

The C.D.C. has modernized public health reporting, but at a smaller scale. In the mid-2010s, the agency used $13 million in Affordable Care Act funds to help state and city health departments go digital. Although that program made some progress, it did not move the country to a completely digital public health reporting system. There have been some smaller one-time grant programs over the last few years, but no long-term funding source for digitization.

“What we learned really fast is that this is a hard problem,” said Dr. Frieden, the former C.D.C. director. “You’ve got hundreds of laboratories and thousands of tests. Nothing is interoperable because they haven’t been mandated to do that.”

Dr. Frieden noted that in other countries, like Britain and Canada, patient data travels with a unique number that identifies whom it belongs to. The United States tried to set up a similar system in the mid-1990s, but it died after Congress passed legislation barring the federal government from creating the new ID numbers.