Researchers have found much higher levels of coronavirus in the brains of mice than in the lungs

• The coronavirus can persist in the brains of mice indefinitely, according to a new study.

• Research may help explain persistent neurological problems in humans, such as dizziness, headaches, or brain fog.

• In some cases, these neurological problems could give rise to chronic illnesses.

• Visit the Business Insider homepage for more stories.

Darius Settles has been fired from the emergency room twice after contracting COVID-19 in June. The first time, she was told to come back if her condition worsened. On his second visit, his blood oxygen levels were normal enough to return him. He died in July, the youngest person killed by the coronavirus in Nashville, Tennessee, around that time.

Situations in which patients look better, get discharged, and then see their condition worsen, have become common during the pandemic. New research suggests it could be linked to infections in the brain.

“People seem to have a very good recovery, lung functions are fine, and we send them home just to find that three days later the patient becomes so severe that he is dead,” said Mukesh Kumar, a virologist at Georgia State University, at Insider. . “This can usually only happen when the brain is involved.”

Kumar recently published a study in the journal Viruses that examines how COVID-19 affects the brains of mice.

His results showed that three days after the mice were infected with the coronavirus, they had high levels of the virus in their lungs. By days five and six, their lungs had started to clear up – but their brains had around 1,000 times more virus than the peak levels found in the lungs. This coincided with the onset of severe symptoms such as difficult breathing, disorientation and weakness.

The virus also triggered an inflammatory response in the brain, marked by the release of chemical signals called cytokines. Under normal circumstances, cytokines tell the immune system to fight infection – but too many cytokines can tell the body to attack its own cells, triggering dangerous levels of inflammation. The brains of the mice in the study showed about 10 to 50 times more cytokines than the lungs.

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In some mice, the reaction caused immediate death. But in mice with milder cases, the virus seemed to hide indefinitely in the brain.

Although the results of studies in mice are not always valid for humans, Kumar suspects that the brain is a major target for the coronavirus.

“Our brains don’t have this good immune response like our lungs or our heart, so every time the virus enters the brain, it can replicate very well,” Kumar said. “He can stay there for a long time.”

Viral replication in the brain could also explain why some coronavirus patients have persistent neurological issues, such as dizziness or brain fog, long after they have tested negative for COVID-19. In some cases, Kumar said, there is a risk that these neurological issues could lead to chronic illnesses such as autoimmune disease, Parkinson’s disease or multiple sclerosis.

“Depending on your immune response or your antibody levels, it could cause low levels of inflammation, or maybe make you prone to other diseases, or maybe reactivate later,” he said. -he declares. “All of these questions are still open as we are only one year away from the pandemic.”

Infections of the nose could reach the brain

COVID-19 is often described as a respiratory disease because the coronavirus first attacks the lungs. But some researchers suspect it may be vascular disease, as some patients develop blood clots, leaky capillaries, and inflamed blood vessels, which can lead to heart damage or a stroke.

A Dutch study of 184 coronavirus patients in the ICU found that almost a third of patients had blood clots. And a July study of 100 patients with COVID-19 found that 78 of them had some degree of heart damage. Studies have also suggested that nearly 2% of patients with COVID-19 have strokes – far more than the rate of strokes in patients with the flu.

But Kumar’s study did not detect any viruses in the blood of infected mice.

Instead, his research showed that the virus entered the brain through the nasal passages, before attacking the central nervous system. Part of this nervous system controls our sense of smell, which may explain why many coronavirus patients find it difficult to smell. Kumar said it’s possible the virus could also reach the brain after entering the mouth, but the nose is a more direct route.

In mice, the coronavirus appeared to have difficulty replicating in organs such as the heart, liver, or kidneys. But infection in the brain can ultimately damage those organs, Kumar said.

“It doesn’t even have to go to all the organs, because while it can go to the brain, there are several parts of the brain that control all the other organs,” he said. “So you may not even need the virus in the lungs to cause lung failure.”

Neurological problems ‘could last a lifetime’

Neurological problems are more common in coronavirus patients than scientists originally thought.

An October study found that 82% of coronavirus patients admitted to a Chicago hospital system in March and April 2020 had neurological symptoms. The problems ranged from relatively minor – headaches, dizziness, and loss of smell – to serious conditions like brain damage, strokes and seizures.

In some cases, these symptoms may persist for at least several months.

A recent study by researchers at the University of Oxford, which is still awaiting peer review, found that 13% of people who contracted COVID-19 were diagnosed with psychiatric or neurological illness within six months after testing positive for the virus. Some patients even had signs of Parkinson’s disease or Guillain-Barré syndrome, a rare autoimmune disease, but these results were not statistically significant.

Kumar said it’s pretty straightforward to tell if a patient has severe neurological disease because the problem will likely show up on an MRI or CT scan. But mild neurological problems are often difficult to identify.

“Unfortunately, based on other studies, this could last a lifetime,” Kumar said. “We know of patients who are still showing symptoms and who were infected a year ago.”

However, his research on the brains of mice is difficult to replicate in humans.

“The patient has to die to find out if the virus is hiding in the brain,” he said.

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