Mr Marshall contracted the more infectious Delta variant of COVID-19 at a Nationals party dinner in Sydney about two weeks ago, and has been unable to return to his hometown of Armidale since.

NSW Health officials have explained the 14-day isolation period has only ever applied to close contacts of someone who has tested positive for the virus.

People who test positive for the virus must remain in isolation from the day they first start to show symptoms; anything from a cold to headaches, a runny nose, shortness of breath or a sore throat.

"In NSW, all close contacts must get tested as soon as possible and self-isolate for 14 days after their exposure to the positive case," a NSW Health spokeswoman said.

"If they develop symptoms during any stage of their self-isolation period, they need to be tested again."

In Mr Marshall's case, he was exposed to the virus on June 21, tested positive two days later and began to show symptoms from the 25^th.

Different isolation requirements apply to people who are infected with COVID-19, the spokeswoman said.

"NSW Health contacts, interviews and assesses people who test positive to COVID-19 and they are managed by clinicians and the Public Health Unit, according to Communicable Diseases Network Australia and NSW Health guidelines," she said.

"Where patients have had symptoms, their release date from isolation is 14 days from their onset of symptoms, provided they have been well for the 72 hours before release.

"Those who test positive are monitored on a regular basis and provided the appropriate health care, including mental health support if required."

Close contacts have to have another test on day seven and day 12 of their isolation period, regardless of any symptoms or past negative tests.

If they don't have a test on or after day 12, they have to remain in isolation for 24 days after their exposure to the positive case.

If close contacts develop symptoms at any point after their isolation period they should get tested immediately, the spokeswoman said.