More than 66,000 people have now been infected in China from a virus that emerged in central Hubei province in December before spreading across the country and some two dozen countries.

Read more: Egypt confirms first coronavirus case in Africa The death toll from the new coronavirus outbreak jumped past 1,500 in China on Saturday as France reported the first fatality outside Asia, fuelling global concerns about the epidemic.

A spotlight was put on the way patients in China are tested for coronavirus when a sudden surge in the number of cases was recorded.

On Thursday, China saw its largest one-day jump in confirmed cases - adding over 15,000- - after health officials in Hubei province, the epicentre of the outbreak, changed their counting criteria to include those "clinically diagnosed".



But the use of lung imaging to uncomfortable lab tests are not always accurate.

In China, the main way to test patients is using the Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) technique.

RT-PCR tests can detect the new coronavirus in patient blood or respiratory tract samples, including those taken from the nose or throat.



Apart from these lab-based tests, health officials have started using lung imaging to "clinically diagnose" patients. If lung images show pneumonia, patients who are already marked as suspected cases are confirmed as infected without the need for a positive test by other means.



Testing capacity remains a challenge in China, said experts, especially as the number of cases continues to soar while researchers race to develop faster and more accurate tests. Read more: How are Arab countries preparing for a possible coronavirus outbreak?



Laboratory tests require special equipment, a clean environment, and "highly skilled staff", said Justman, to prevent samples from becoming contaminated.

Another issue with current tests is speed - RT-PCR tests can take two to three hours, said John Nicholls, clinical professor in pathology at the University of Hong Kong.

And if hospitals have a limited daily capacity to run tests, that in turn becomes a "ceiling" for monitoring the spread of the epidemic, said Ben Cowling from Hong Kong University's School of Public Health.



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