A second US evacuee from China has been diagnosed with coronavirus after the CDC admitted its test kits are flawed.

The new case announced by the Centers for Disease Control and Prevention (CDC) on Wednesday brings the total number of confirmed coronavirus cases in the US to 14.

The patient was aboard a flight from Wuhan, the city at the center of the outbreak, that arrived at Marine Corps Air Station Miramar in Southern California last week. They are now in isolation at a hospital in San Diego.

Also in isolation is a woman who was mistakenly released because of a mislabeled sample that hadn't been tested for coronavirus. She was returned to the hospital on Monday after testing positive for the virus and is expected to make a full recovery.

The latest confirmed case comes hours after a senior CDC official Nancy Messonnier revealed that a number of coronavirus test kits sent out by US health authorities to labs across the country are faulty.

The CDC began shipping 200 test kids nationwide on February 5 to speed up the diagnosis of US cases of the virus dubbed COVID-19.

But the labs reported that while performing a verification procedure they realized the kits were returning inconclusive results, meaning neither positive nor negative, Messonnier said.

Now, the CDC is remaking the component they believe to be at fault, a setback for the long-awaited tests meant to cut down wait times for test results.

A second US evacuee from China has been diagnosed with coronavirus, the CDC confirmed Wednesday. The patient was aboard a flight from Wuhan, the city at the center of the virus outbreak, that arrived at Marine Corps Air Station Miramar in Southern California last week. Passengers on that flight are seen stepping off the plane

The latest confirmed case came hours after a senior CDC official revealed that a number of coronavirus test kits sent out by US health authorities to labs across the country are faulty

It is unclear whether the second evacuee's diagnosis was affected by the faulty tests. No details have been released that patient.

Messonnier has said that the mix-up with the first evacuee was unrelated to the test kit issue.

In quality assurance tests, some labs are reporting that the screening kit is returning inconclusive results on cell samples that should come back positive or negative.

These tests, Messonnier said, have not yet been used to screen actual patient samples, so they have not created any such issues.

In California, officials initially believed that the first Wuhan evacuee, had been tested, with negative results, and was thus sent back to quarantine on Marine Corps Station Miramar (MCS Miramar).

However, the woman's sample had not actually been tested yet, due to what Messonnier chocked up to a labeling issue.

'It isn't that someone else was falsely identified as positive, it was that [the test] wasn't initially run,' she said.

'The mishap was unfortunate but it was corrected from happening again in the future by adding additional quality control.'

When the patient's sample was actually run, she was quickly identified as positive for coronavirus and brought back to the hospital at UC San Diego for treatment.

In the meantime, Messonnier said that infection control precautions were taken. A second person was also transported to the hospital for testing.

Senior CDC official Dr Nancy Messonnier (pictured) said none of the faulty tests were used on any of the 14 American patients confirmed to have coronavirus

COVID-19 has sicked more than 45,200 people and killed 1,116 worldwide as of Wednesday

Separately, the CDC is now working to get a new batch of test kits - or at least replacements for the component they think is defective - reissued to more than 100 authorized labs across the US.

'We're looking into what's wrong...We think that the issue at the stage, can be explained by one reagent that isn't performing as it should, consistently,' she said, referring to one the substances used in the kit.

'And that's why we are remanufacturing that reagent.'

For now, the testing of all patient specimens will continue to be carried out at the CDC's headquarters in Atlanta, Georgia.

'Speed is important, but equally or more important in this situation is making sure lab results are correct,' said Messonnier.

The US is shipping the test kit to 36 countries that have placed orders, and each kit can be used approximately 700 to 800 times.