More stories about the coronavirus outbreak.

LOS ANGELES — The four-day delay in testing a Northern California patient who appears to be the first in the United States to contract the coronavirus from community contact highlights growing questions about the federal government’s testing policies and protocols as the virus continues to spread.

A growing number of experts have said problems with the test process — including ineffective test kits and restrictive rules on who gets tested — could be fueling the undetected spread of the virus.

“When you miss cases, you can’t isolate them, test their families or get a hold on this before it keeps spreading,” said Jennifer Nuzzo, an epidemiology expert at the Johns Hopkins Center for Health Security.

Until Thursday, the Centers for Disease Control and Prevention restricted coronavirus testing to patients with clear symptoms of infection who have either traveled to China recently or who have been in contact with someone who has tested positive for the virus. As the virus outpaced detection efforts around the world, that gateway to testing proved far too narrow.

As early as last week, doctors at the UC Davis Medical Center suspected a coronavirus case and immediately requested testing from the CDC. But it was another four days before the test was done. During that time, others in the area could have been exposed to the virus.

On Thursday, the CDC expanded the criteria for who qualified for testing to include sick patients who had traveled to Iran, Italy, Japan and South Korea. They will also test severely ill patients with acute lower respiratory sickness who are hospitalized, even those who have no known link to the coronavirus outbreak.

The CDC faces growing political backlash.

California Sen. Dianne Feinstein on Thursday called on the White House to start rapid testing of all suspected cases, saying the identification of coronavirus patients quickly is essential to limiting the spread.

Gov. Gavin Newsom said California is in desperate need of test kits. The state has 200 kits for both diagnostic and surveillance purposes, but federal officials say more will arrive in the coming days, he said.