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 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 increasingly 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.

RAT result figures are expected to be counted by the state from later this week after upgrades are made to the Service NSW app.

Service NSW is currently developing a mechanism to allow people to upload their positive RAT results and link them to health advice and services.

NSW Health continues to urge anyone who is eligible to book in for a vaccine booster.

"People aged 18 years and over are eligible for a booster if they had their second dose at least four months ago," the department daid.

"We urge people to get their booster dose as soon as they are eligible, to best protect themselves, their loved ones and the community from the ongoing transmission of COVID-19. We also strongly recommend that people aged 12 years and over who are severely immunocompromised have a third primary dose of vaccine from two months after their second dose."

Vaccination for children aged between 5 and 11 also began in NSW on Monday morning.

The federal government's online vaccine clinic finder can be used to locate a clinic and book a jab.

COVID testing sites are open in Wagga seven days a week at the MLHD's Murray Street clinic, between 8am and 4pm, and at the drive-through site at Wagga Showground between 7.30am and 12.30pm.

Laverty Pathology also operates a drive-through clinic in the Riverina Playhouse car park, off Cross and Tarcutta streets, between 8am and noon on weekdays.

Appointments are required for a COVID test at the GP-led respiratory clinic at Glenrock in Glenfield Park, where people can be tested between 9am and 5pm on weekdays.

The community is reminded to monitor for symptoms and if they occur, stay home and isolate until you can access a test.

For further testing locations across the region, go to www.mlhd.health.nsw.gov.au, or for help accessing a test, call the Murrumbidgee COVID-19 Hotline 1800 831 099.

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