The number of novel coronavirus cases in the US surged past 1,000 after public health experts criticised authorities for downplaying the epidemic and lagging behind in testing efforts.

At least 28 people have died and 1,025 people have been infected, according to a running tally by Johns Hopkins University — nearly double the 550 total confirmed cases the day before.

The rise is linked to an expansion in testing as the bulk of diagnoses have shifted from federal to state laboratories.

Epidemiologists have said faulty test kits coupled with a diagnostic strategy that initially targeted too few people allowed the disease to spread beyond US authorities' ability to detect it.

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