- Coronavirus may remain indefinitely in the brain of rats, according to a new study.
- The research may help explain persistent neurological problems in humans, such as dizziness, headaches or brain fog.
- In some cases, these neurological problems can give rise to chronic diseases.
- Visit the Business Insider home page for more stories.
Darius Settles was sent home from the emergency room twice after contracting COVID-19 in June. The first time, he was told to return if his condition worsened. On her second visit, her blood oxygen levels were normal enough to be discharged again. He died in July, the youngest person killed by the coronavirus in Nashville, Tennessee, at that time.
Situations in which patients look better, are discharged and then see their condition worsen became common during the course of the pandemic. New research suggests it may be related to infections in the brain.
“People seem to have a very good recovery, lung function is well and we sent them home only to find that three days later, the patient becomes so severe that he died,” Mukesh Kumar, a virologist at Georgia State University, said. 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 brain of mice.
Their results showed that three days after the mice were infected with the coronavirus, they exhibited high levels of the virus in their lungs. On days five and six, his lungs started to clear – but his brains showed about 1,000 times more viruses than the maximum levels found in his lungs. This coincided with the arrival 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 many cytokines can instruct 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.
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 the mouse studies are not always true for humans, Kumar suspects that the brain is the primary target of the coronavirus.
“Our brain doesn’t have a good immune response like our lungs or heart, so whenever the virus goes to the brain, it can replicate very well,” said Kumar. “You can stay there for a long time.”
Viral replication in the brain may also explain why some patients with coronavirus have persistent neurological problems, 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 problems will lead to chronic diseases, such as autoimmune disorders, Parkinson’s or multiple sclerosis.
“Depending on your immune response or antibody levels, it can cause low levels of inflammation, or maybe make you prone to other diseases, or maybe reactivate later,” he said. “All of these issues are still pending because we are still only a year away from the pandemic.”
Nose infections can travel to the brain
A woman misuses her face mask in Rome, Italy, on April 29, 2020.
Andreas Solaro / AFP / Getty Images
COVID-19 is often described as a respiratory disease, since the coronavirus attacks the lungs first. But some researchers suspect it may be a vascular disease, as some patients develop blood clots, leaking capillaries and inflamed blood vessels, which can cause heart damage or stroke.
A Dutch study of 184 patients with coronavirus in the ICU found that almost a third of patients had blood clots. And a July study of 100 COVID-19 patients found that 78 of them had some degree of cardiac damage. Studies have also suggested that almost 2% of COVID-19 patients have strokes – far more than the stroke rate among influenza patients.
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 patients with coronavirus find it difficult to smell. Kumar said it is possible that the virus could also reach the brain after entering the mouth, but the nose is a more direct route.
In rats, the coronavirus appeared to have trouble replicating itself in organs such as the heart, liver or kidneys. But an infection in the brain can damage these organs, said Kumar.
“You don’t even have to go to all the organs, because you can go to the brain, there are several parts of the brain that control all the other organs,” he said. “So it may also be possible that you don’t even need the virus in your lungs to cause lung failure.”
Neurological problems ‘can last a lifetime’
A patient who has recovered from COVID-19 gestures next to his son when he leaves the Juarez Hospital in Mexico City, Mexico, July 27, 2020.
Edgard Garrido / Reuters
Neurological problems are more common among coronavirus patients than scientists originally thought.
An October study found that 82% of coronavirus patients admitted to a hospital network in Chicago in March and April 2020 had neurological symptoms. The problems ranged from relatively minor ones – headaches, dizziness and loss of smell – to serious conditions like brain damage, strokes and seizures.
In some cases, these symptoms can last for at least several months.
A recent study by researchers at Oxford University, which is still awaiting peer review, found that 13% of people who received COVID-19 were diagnosed with psychiatric or neurological disease six months after the test was positive for the virus. Some patients even showed signs of Parkinson’s disease or Guillain-Barré syndrome, a rare autoimmune disease, but these results were not statistically significant.
Kumar said it is quite simple to say whether a patient has a serious neurological condition, as the problem is likely to show up on an MRI or CT scan. But mild neurological problems are often difficult to identify.
“Unfortunately, based on other studies, it can last a lifetime,” said Kumar. “We know of patients who still have symptoms that were infected a year ago.”
The research he did on the brains of mice, however, is difficult to replicate in humans.
“The patient has to die to find out if the virus is hiding in the brain,” he said.