SIOUX FALLS, S.D. -- Expanded coronavirus testing in South Dakota is paying off, revealing the previously undetected spread of the virus in many of the state's counties, nearly half of which have a confirmed case.

South Dakota reported 22 new cases on Sunday, March 29, bringing the state's total to 90, its single biggest daily jump in confirmed cases thus far. The state has nearly doubled its known number of cases since Thursday.

Two health system labs in Sioux Falls -- Sanford Health and Avera Health -- started processing coronavirus tests last week, greatly expanding the state's capacity, previously restricted to the state public health lab in Pierre, which has a much more limited ability to test for the virus.

By March 23, the state lab had processed about 1,000 tests in the previous weeks. A week later, state, private and in-hospital labs have processed just over 3,200 tests.

Testing has now found cases of the coronavirus in residents of 28 of the state's 66 counties, double the number of counties with a known case since Wednesday. On Sunday alone, testing revealed confirmed cases in five new counties: Clark, Clay, Fall River, Roberts and Turner, according to the state Department of Health's coronavirus information page.

Case counts continue to climb in the hardest-hit Huron and Sioux Falls areas. The two counties that contain Sioux Falls -- Minnehaha and Lincoln -- added five new cases Sunday for a combined total of 29. Beadle County, home to Huron, added four cases for a total of 20.

New testing has also found new counties where the virus is jumping from person to person undetected, known as community spread. State officials first announced on March 24 they had confirmed evidence of community spread in Beadle County on March 24. Nearly a week later, they've confirmed community spread in 10 counties.

Cases not classified community spread means public health officials know where the diagnosed individual likely caught the disease, either from travel to highly infected areas outside the state or from contact with someone already diagnosed with COVID-19, the respiratory illness caused by the coronavirus.

Of South Dakota's 90 known cases, 29 have recovered. One, a Pennington County man in his 60s, died from the illness in Davison County March 10.

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