Doctors are bracing for a rapid rise in U.S. coronavirus cases this week as state and local public health labs ramp up testing after weeks of delays due to a flawed test by the U.S. Centers for Disease Control and Prevention.

The number of confirmed U.S. cases topped 100 Tuesday, including nine deaths in Washington.

A Seattle-area researcher said his genetic analysis shows the virus probably circulated undetected in the state for six weeks. That means more people in the community, even those who have not traveled to endemic regions, might face risk of exposure.

The CDC initially developed and mailed testing kits with three components, or reagents, to detect the COVID-19 virus. Some states had trouble validating one of three components in the kits. Friday, a CDC official said the agency reviewed the glitch and determined using two components accurately will detect coronavirus.

CDC officials said all state and local public health labs and qualified private labs should be able to test by the end of this week. The agency relaxed its strict testing guidelines.

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The combination of functioning testing kits and robust testing capacity at state and local labs should give public health officials and doctors this week a better idea on the scope of the virus' spread in the USA and focus how to marshal limited resources.

Dr. Amesh Adalja, a senior scholar at Johns Hopkins Center for Health Security, said the testing glitch "left the United States without adequate testing capacity longer than it should have."

He said widespread testing is important because it can pick up mild cases of coronavirus, not just more severe examples of people needing hospital care.

He cited the example of a Snohomish County, Washington, high school student with flu-like symptoms who had not traveled but became ill with coronavirus. The student stayed home from school and sought medical care before returning to school Friday because he felt better. Later that day, he learned tests from earlier that week revealed coronavirus.

Such testing showed the virus appears to circulate among nontravelers. It also showed people might have a mild form of the respiratory disease.

"People are going to panic when they see the number of cases go up," Adalja said. "But it's important to remember we expect it to go up. People shouldn't panic ... even when they find cases in their state or in their city, because (cases) are likely everywhere."

Former CDC Director Tom Frieden agreed the priority is to get tests to communities and detect the virus and prevent its spread.

"There’s clearly been a glitch in that process with a problem with some of the tests," said Frieden, who heads a group called Resolve to Save Lives. "The point now is to get the test kits and test capacity out as widely as possible."

He said it's important that the federal government reviews the delayed test kit rollout to address any problems.

"I think it will be important when things quiet down (and) there is time, to have an after-action review and see what went wrong and see how that can be prevented in the future," he said.

'Beginning stages of a pandemic'

Robert Murphy, executive director of the Institute for Global Health at Northwestern University Feinberg School of Medicine, said federal health officials should have tested more aggressively to better track cases. By detecting cases through more widespread testing, they could have slowed community spread.

"The opportunity was missed," Murphy said. "There were delays, and now there are going to be more cases."

The CDC announced it would begin testing people with flu-like symptoms in Chicago, Los Angeles, New York, San Francisco and Seattle to detect possible spread of coronavirus. Such testing should begin this week, and there are plans to expand surveillance to all 50 states, Nancy Messonnier, director of the CDC's National Center for Immunization and Respiratory Diseases, said Friday.

Widespread testing can help public health officials learn how lethal the virus might be. In China, where more than 80,000 people have been infected, the fatality rate exceeds 2%, but that rate is much lower outside China. South Korea's aggressive testing identified more than 5,000 cases – the world's second-highest total – but the nation's 28 deaths give it a fatality rate of about .5%, according to figures on Johns Hopkins' coronavirus tracker.

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Adalja said more robust testing will reveal more cases and will give scientists a better idea about the severity of the outbreak. More cases, particularly mild cases, might unmask the virus as far less lethal than feared and allow the public to "breathe a sigh of relief," he said.

"That will decrease the angst some people have over the severity of what's going to happen," Adalja said. "We're in the beginning stages of a pandemic. So it's coming. It's really important we right-size the response by knowing what the true severity is."

He suggested more testing might inform public health officials how to respond. That might include investing more on testing and ensuring hospitals are prepared, while spending less on labor-intensive measures such as tracing the contacts of infected individuals and monitoring travel restrictions.

Members of Congress seek answers about the nation's testing capacity and delays in getting working kits to public health labs.

Rep Mark Pocan, D-Wis., sent a letter Monday to the CDC raising questions about the agency's response and how it publicly discloses testing cases.

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