Covid-19 can cause brain cells to fuse, study finds

Infection with the SARS-CoV-2 virus can cause brain cells to fuse, initiating malfunctions that lead to chronic neurological symptoms, according to a study.

SARS-CoV-2, the virus that causes COVID-19, has been detected in the brains of people with "long Covid" months after their initial infection.

The new research, published in the journal Science Advances. explored how SARS-CoV-2 alters the function of the nervous system.

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"We discovered Covid-19 causes neurons to undergo a cell fusion process, which has not been seen before," said Professor Massimo Hilliard from The University of Queensland, Australia.

"After neuronal infection with SARS-CoV-2, the spike S protein becomes present in neurons, and once neurons fuse, they don't die. They either start firing synchronously, or they stop functioning altogether," Hilliard said.

The researcher likened the role of neurons to that of wires connecting switches to the lights in a kitchen and a bathroom.

"Once fusion takes place, each switch either turns on both the kitchen and bathroom lights at the same time, or neither of them," Hilliard said.

"It's bad news for the two independent circuits," he added.

The discovery offers a potential explanation for persistent neurological effects after a viral infection, the researchers said.

"In the current understanding of what happens when a virus enters the brain, there are two outcomes—either cell death or inflammation," said Ramon Martinez-Marmol from The University of Queensland.

"But we've shown a third possible outcome, which is neuronal fusion," Martinez-Marmol said.

The researchers noted that numerous viruses cause cell fusion in other tissues, but also infect the nervous system and could be causing the same problem there.

"These viruses include HIV, rabies, Japanese encephalitis, measles, herpes simplex virus and Zika virus," Martinez-Marmol said.

"Our research reveals a new mechanism for the neurological events that happen during a viral infection. This is potentially a major cause of neurological diseases and clinical symptoms that is still unexplored," he added.