(CNN)The lines for Covid-19 testing are long from New York to Miami-Dade County again, and good luck finding an at-home test in some parts of the country.
As the Omicron variant spreads faster than any other coronavirus variant before it, the Biden White House has been pushing to make tests more accessible. They've made this push for months, but critics say it is not nearly enough.
Supply just can't keep up with demand, and yet with Omicron being so much more infectious, testing will become more important than ever, said Mara Aspinall, professor of practice at the College of Health Solutions at Arizona State University.
"We are at a very, very precarious moment," Aspinall said. "Testing is our only exit strategy out of all of this."
If people don't test, it puts the country at risk for a greater spread of the disease.
"Testing is the core because without that, there's no way people will isolate," Aspinall said.
Most disease in the US now is still being caused by the Delta variant.
In addition to the usual demand for tests, the current increase stems from people with a few different needs, she said. Some have symptoms, and with the flu and other viruses floating around, they want to know if they have Covid-19. Others want to test before they get on a plane or spend time with family over Christmas. Both are important reasons to get a test, she said, but the test supply is just not ready for them.
"As recently as a week ago, I thought maybe we had enough tests, but if Omicron ends up at 200,000 or 300,000 cases a day, we likely don't have enough tests," Aspinall said. "At each stage we thought it was close to enough, and now we know it's not enough."
Last week White House Covid-19 Response Coordinator Jeff Zients insisted that "there's plenty of free testing across the country."
Since then, cases have spiked dramatically in some states. The US is now averaging 121,707 new Covid-19 cases each day, according to Johns Hopkins University. New case rates have been holding steady over the past week, but at levels last seen in September at the end of the summer surge. And cases are increasing at a much faster clip in parts of the Northeast, Midwest and South.
White House Press Secretary Jen Psaki scoffed last week when asked if tests should be free and given out, available everywhere.
"Should we just send one to every American?" she asked.
However, similar initiatives already exist at a local level in some cities.
On Thursday, New York City Mayor Bill deBlasio announced the city would begin distributing half a million at-home rapid Covid-19 tests for free through community organizations. There are also programs in Ohio that distribute rapid tests through public libraries. In Atlanta, a program called Say Yes! Covid Test sends tests to homes in certain zip codes.