Virus World

Bird flu is infecting the brains of wild mammals such as foxes and raccoons and may be making them behave in unusual ways, according to a study in the US. Out of 57 live mammals found to be infected, 53 had neurological symptoms, such as seizures, problems with balance, tremors and a lack of fear of people. The risk to people appears to be low. “There isn’t yet any evidence that red foxes or other wild mammals …

SARS-CoV-2 generally attacks the lungs, but researchers are also stressing its effects on the brain in a fraction of patients. Newly described case reports add to growing evidence that COVID-19 infections can result in severe, long-lasting neurological complications—including inflammation, psychosis, delirium, nerve damage, and strokes—even among patients experiencing mild cases of the virus with few other symptoms. In some instances, the new study claims, these neurological effects were the first manifestation of the disease. In a paper published today (July 8) in the journal Brain, neurologists in the UK noted an uptick this spring in cases of a potentially fatal condition called acute disseminated encephalomyelitis (ADEM). While ADEM is usually diagnosed in younger children after a viral infection, researchers at the college’s Institute of Neurology tell The Guardian that they saw two or three cases per week among coronavirus patients during April and May. Ordinarily, the hospital sees about two ADEM cases per month among adults. “We’re seeing things in the way Covid-19 affects the brain that we haven’t seen before with other viruses,” says Michael Zandi, a consulting neurologist at the university’s hospital and the study’s senior author. “What we’ve seen with some of these Adem patients, and in other patients, is you can have severe neurology, you can be quite sick, but actually have trivial lung disease,” he adds.

COVID-19 is primarily a respiratory disease that attacks the lungs, but it has also manifested seemingly unrelated symptoms, such as a loss of taste and smell or memory loss, that can persist for months beyond the initial diagnosis. These oddities suggest a neurological source. The study detailed the neurological symptoms of 43 patients hospitalized in the National Hospital for Neurology and Neurosurgery in London with confirmed or suspected cases of COVID-19. A dozen were diagnosed with inflammation of the central nervous system, including nine cases of ADEM. A further 10 patients experienced delirium or psychosis. Eight patients suffered strokes, including one that was fatal, and another eight had peripheral nerve damage. At least two patients also developed strange behaviors shortly after being discharged from the hospital. One woman, as described in the paper, repeatedly donned and took off her coat, and began hallucinating lions and monkeys inside her home. Another woman became drowsy and ultimately needed emergency surgery to relieve the pressure on her brain...

As if the symptoms of COVID-19 were not disturbing enough, physicians have noted a rare neurological condition that emerges during some severe cases of this viral infection. The patient in the case report (let’s call him Tom) was 54 and in good health. For two days in May, he felt unwell and was too weak to get out of bed. When his family finally brought him to the hospital, doctors found that he had a fever and signs of a severe infection, or sepsis. He tested positive for SARS-CoV-2, the virus that causes COVID-19 infection. In addition to symptoms of COVID-19, he was also too weak to move his legs. When a neurologist examined him, Tom was diagnosed with Guillain-Barre Syndrome, an autoimmune disease that causes abnormal sensation and weakness due to delays in sending signals through the nerves. Usually reversible, in severe cases it can cause prolonged paralysis involving breathing muscles, require ventilator support and sometimes leave permanent neurological deficits. Early recognition by expert neurologists is key to proper treatment.

We are neurologists specializing in intensive care and leading studies related to neurological complications from COVID-19. Given the occurrence of Guillain-Barre Syndrome in prior pandemics with other corona viruses like SARS and MERS, we are investigating a possible link between Guillain-Barre Syndrome and COVID-19 and tracking published reports to see if there is any link between Guillain-Barre Syndrome and COVID-19.

Some patients may not seek timely medical care for neurological symptoms like prolonged headache, vision loss and new muscle weakness due to fear of getting exposed to virus in the emergency setting. People need to know that medical facilities have taken full precautions to protect patients. Seeking timely medical evaluation for neurological symptoms can help treat many of these diseases.

Guillain-Barre syndrome occurs when the body’s own immune system attacks and injures the nerves outside of the spinal cord or brain – the peripheral nervous system. Most commonly, the injury involves the protective sheath, or myelin, that wraps nerves and is essential to nerve function. Without the myelin sheath, signals that go through a nerve are slowed or lost, which causes the nerve to malfunction...

Gut microbes produce compounds that prime immune cells to destroy harmful viruses in the brain and nervous system. The findings suggest that having healthy and diverse microbiota is essential for quickly clearing viruses in the nervous system to prevent paralysis and other risks associated with diseases such as multiple sclerosis. 

"We wanted to investigate whether gut microbes could alter the immune response to a virus in the central nervous system and whether this affects the amount of damage the virus causes," says one of the lead authors David Garrett Brown, a graduate research assistant in the Department of Pathology at University of Utah Health, Salt Lake City, US.

To do this, Garrett Brown and co-lead author Ray Soto looked at the effect of Mouse Hepatitis Virus, a virus that infects cells in the mouse nervous system and causes multiple-sclerosis type symptoms, on two groups of mice: some with normal gut microbes and some that were bacteria-free. They found that bacteria-free mice had a weak immune response, were unable to eliminate the virus and developed worsening paralysis, while those with normal gut bacteria were better able to fight off the virus. Mice treated with antibiotics before the onset of disease were unable to defend themselves. They also had fewer immune cells called microglia, which help flag viruses for destruction by other immune cells.

The studies were published today in eLife:

 https://doi.org/10.7554/eLife.47117