Dödligt virus från Kina orsakar panik (SARS-CoV-2, COVID-19)

The coronavirus targets the lungs foremost, but also the kidneys, liver and blood vessels. Still, about half of patients report neurological symptoms, including headaches, confusion and delirium, suggesting the virus may also attack the brain.
A new study offers the first clear evidence that, in some people, the coronavirus invades brain cells, hijacking them to make copies of itself. The virus also seems to suck up all of the oxygen nearby, starving neighboring cells to death.

Dr. Zandi and his colleagues published research in July showing that some patients with Covid-19, the illness caused by the coronavirus, develop serious neurological complications, including nerve damage.
In the new study, Dr. Iwasaki and her colleagues documented brain infection in three ways: in brain tissue from a person who died of Covid-19, in a mouse model and in organoids — clusters of brain cells in a lab dish meant to mimic the brain’s three-dimensional structure.
Other pathogens — including the Zika virus — are known to infect brain cells. Immune cells then flood the damaged sites, trying to cleanse the brain by destroying infected cells.
The coronavirus is much stealthier: It exploits the brain cells’ machinery to multiply, but doesn’t destroy them. Instead, it chokes off oxygen to adjacent cells, causing them to wither and die.
The researchers didn’t find any evidence of an immune response to remedy this problem. “It’s kind of a silent infection,” Dr. Iwasaki said. “This virus has a lot of evasion mechanisms.”
These findings are consistent with other observations in organoids infected with the coronavirus, said Alysson Muotri, a neuroscientist at the University of California, San Diego, who has also studied the Zika virus.
The coronavirus seems to rapidly decrease the number of synapses, the connections between neurons. “Days after infection, and we already see a dramatic reduction in the amount of synapses,” Dr. Muotri said. “We don’t know yet if that is reversible or not.”
The virus infects a cell via a protein on its surface called ACE2. That protein appears throughout the body and especially in the lungs, explaining why they are favored targets of the virus.
Previous studies have suggested, based on a proxy for protein levels, that the brain has very little ACE2 and is likely to be spared. But Dr. Iwasaki and her colleagues looked more closely and found that the virus could indeed enter brain cells using this doorway.
“It’s pretty clear that it is expressed in the neurons and it’s required for entry,” Dr. Iwasaki said.