(NewsNation) — Chinese scientists are experimenting with a mutant COVID strain that reportedly has a 100% mortality rate in mice, bringing back memories of 2020 and the start of the pandemic.

The strain attacks the brains of mice engineered to reflect a similar genetic makeup to humans, and most mice lived just eight days after being infected.

Researchers reported the mice lost weight, became sluggish and adopted a hunched posture with their eyes turning completely white the day before they died.

Dr. Kristin Englund cautioned the study was small and the paper is a preprint, which means it has not been peer-reviewed yet.

“It is important that we do listen to the data coming out of China because they do a lot of research on coronaviruses,” Englund told NewsNation.

Humanized mice are bred so their immune systems are similar to humans, but there are still some major differences.

Englund added that the mice were modified significantly to have more ACE receptors, which COVID latches onto to get into cells.

“So it’s really not human-like,” she said.

The biggest concern is what kind of research is being done with the strain and the possibility the virus could leak from the lab. Some have suggested the COVID-19 pandemic was itself the result of a lab leak due to lax security in China.

Dr. Aileen Marty, an infectious disease doctor at Florida International University, said there is no need for alarm.

“The studies themselves, especially if they are well done and well contained in appropriate laboratories, are very useful for helping us get ahead of natural changes such that we can produce appropriate monoclonal antibodies, different types of enzyme inhibitors like protease inhibitors and even produce better vaccines ahead of time before there’s a major problem if it happens spontaneously,” she said.

Marty said it would be critical for the global community to ensure everything is being done safely in China to contain the research to the lab.