Kiwi microbiologist Dr Siouxsie Wiles wants everyone who participated in any of New Zealand's Black Lives Matter (BLM) marches on Monday to self-isolate for 14 days.
Thousands of people turned up to marches in cities including Auckland, Wellington and Christchurch, making it more difficult to enforce physical distancing of one metre.
To stop a new surge of COVID-19 cases in New Zealand, Dr Wiles wants all participants to go into self-isolation.
"Absolutely gutted to see so many people joined the NZ BLM gatherings/marches without taking COVID precautions. If you went today, please, please, please self isolate for the next 14 days. The last thing any of us want is to see a surge in cases," she wrote on Twitter.
Earlier on Monday, she urged anyone who did want to participate in the marches to wear masks and obey physical distancing rules, or stay home if they felt even slightly unwell. She said people in large groups who are talking loudly or shouting create a perfect combination for the virus to spread.
One person replied to her saying the majority of people he saw were wearing masks, and he wondered if there were any other measures he could've taken. She responded by saying masks don't offer full protection from infections, they just help reduce the spread if you are infected.
"You should self isolate if you were surrounded by people not masked," she added.
The protest organisers have created an online contact tracing form for people who went to any of New Zealand's marches in case there is an outbreak.