Wodonga has recorded 89 cases of COVID-19 in the past 24 hours.

In Indigo shire, 40 new cases were recorded while 53 new cases were recorded in Wangaratta, 33 in Alpine and five in Towong.

There are 446 active cases in Wodonga, 166 in Indigo, 275 in Wangaratta, 158 in Alpine and 40 in Towong Shire.

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A Riverina resident has died from COVID-19 and hundreds more have officially been diagnosed with COVID-19 on the state's deadliest day of the pandemic.

An even 500 cases of the virus were detected in the Murrumbidgee Local Health District [MLHD] in the 24 hours to 8pm Sunday, NSW Health has confirmed.

It comes as the state recorded 20,293 new cases and 18 people died from COVID-19 in the same time period, the worst death toll in a day for NSW.

One of those was a member of the Riverina community, NSW Health revealed in the Monday morning update. NSW Health has not provided details of where in the Riverina the person lived.

"NSW Health expresses its sincere condolences to their loved ones," the department said.

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NSW chief health officer Dr Kerry Chant said on Monday morning the downward shift in case and test figures reflects the rise of rapid antigen test [RAT] use in detecting the virus.

"As incresingly people follow NSW Health's advice to use rapid antigen testing for diagnosing COVID-19, the number of PCR tests will underestimate the true number of people who have tested positive," NSW Health said.

The MLHD is managing an outbreak at Temora Hospital, where four people have been diagnosed with COVID.

Three patients admitted to the facility have acquired the infection during their stay, and one person presented to the hospital's emergency department.

All four have been transferred to Wagga Base Hospital and Temora Hospital is closed to visitors until further notice.

As of Sunday afternoon, 26 people were being cared for in MLHD hospitals.