Surviving an epidemic is not always the end of the story. Some viruses can have health effects that span decades, culminating in a series of devastating diseases.
In the 1960s, epidemiologists studying the long-term warning of survivors of the 1918 Spanish flu began noticing something unusual. They found that people born between 1888 and 1924 – meaning they were infants or young adults at the time of the epidemic – were less likely to develop Parkinson’s disease at some point in their lives than at different times. people are born.
This is an amazing discovery. Although doctors have documented the potential neurological effects of influenza infection for centuries — medical reports say they date back to 1385 — the widespread outbreak of the Spanish flu, which has infected nearly 500 million people worldwide, means scientists can point to pandemics. As the reason for the high incidence of certain diseases.
In recent years, survivors of HIV, West Nile virus, Japanese encephalitis, Coxsackie virus, western equine encephalitis virus, and Epstein-Barr virus outbreaks have been at increased risk of developing Parkinson’s disease.
Neuroscientists trying to understand why this happens believe that each of these viruses is able to enter the brain and, in some cases, destroy the fragile structures that control motor coordination, called “basal ganglia,” and this triggers a degenerative process that can lead to paralysis. tremor
Scientists are now keen to monitor whether the current pandemic will also lead to higher rates of Parkinson’s disease in the coming decades.
“We don’t know what’s going to happen, but we have to keep in mind that it could,” said Patrick Brintin, a Parkinson’s disease researcher at the Van Andel Institute in Grand Rapids, Michigan, USA. Central nervous system deficits, including loss of smell and taste, brain fog, depression and anxiety. These numbers are alarming.”
While coronaviruses can invade brain tissue, scientists are still not sure whether this contributes to the development of neurodegenerative diseases. Coronaviruses are often referred to as “hit and run viruses” because they tend to cause fairly short-lived illnesses, even if, in some cases, the patient dies. By contrast, DNA viruses, such as the Epstein-Barr virus, can remain in the body permanently and are more associated with long-term disease.
But there have been some signs in the past that the impact of the coronavirus may be greater than we thought. In the 1990s, Canadian neurologist Stanley Fahn published a study that identified cold-causing coronavirus antibodies in cerebrospinal fluid in Parkinson’s patients.
Over the past year, scientists like Brendon have become concerned about the emergence of a small number of case studies describing patients who experienced what doctors call acute Parkinson’s disease — such as tremors — after contracting the coronavirus, muscle stiffness, and slurred speech. .
Other studies have found that some coronavirus patients suffer from one of the most dangerous systems in the body, known as the “kynurenine pathway”, which extends from the brain to the intestine to produce many of the essential amino acids necessary for brain health. But when destroyed, it can lead to a buildup of toxins that are thought to play a role in Parkinson’s disease.
However, other neurologists have warned that it is too early to prove any link between the coronavirus and Parkinson’s disease.
Alfonso Fasano, a professor of neuroscience at the University of Toronto, pointed out that the cases of acute Parkinson’s disease described may include only patients who are already in the early stages of the disease, and that infection with the new Corona virus will only accelerate or “reveal” symptoms.
He said: “So far we have discussed dozens of cases and often we lack detailed information. It is true that what we call Parkinson’s disease after encephalitis can happen after a viral infection, but epidemics are different from each other, Spain, for example, causes influenza to be A completely different virus.
However, many believe that if cases gradually increase over the next few years, continuous monitoring of people who were previously infected with the coronavirus for any symptoms similar to Parkinson’s disease is warranted.
But Parkinson’s disease isn’t the only problem. Experts around the world are trying to find out if the coronavirus could trigger a hidden wave of other illnesses linked to the damage the virus does to the body’s immune system. If that happens, it would have major public health implications, but it could also help us find new ways to detect these diseases early and even pave the way for new treatments and vaccines.
In the spring of 2020, Francesco Rubino, an expert on metabolism and obesity at King’s College London, began hearing increasing reports of coronavirus patients with abnormal blood sugar levels despite no prior history of diabetes.
At the same time, doctors are also pointing out that patients who already have diabetes appear to be particularly vulnerable to contracting the coronavirus. Rubino was curious if the odd relationship suggested the coronavirus was directly affecting the pancreas, a complex organ that contains beta cells that produce insulin, the hormone that helps the body metabolize sugar molecules from the blood.
Rubino created a global database called the Coronavirus and Diabetes Registry to track and understand these patients. The database, which has tracked 700 cases so far over the past year, hopes the data will help answer a difficult question that has baffled scientists for years: whether the virus directly causes type 1 diabetes.
In the past, type 1 diabetes — a chronic disease that usually develops in childhood or adolescence in which the pancreas no longer produces insulin steadily — has been linked to Coxsackie B virus, rubella, cytomegalovirus, mumps, and other related viruses. Scientists believe that these viruses may infect the pancreas by escaping from the lungs or infiltrating blood vessels from the intestines.
In 2015, researchers at the Oslo Diabetes Research Center found persistent, low-grade viral infection in beta-cells taken from pancreatic tissue biopsies from people with newly diagnosed type 1 diabetes, but the cases were too few to establish an important relationship.
“Before that, there were epidemics that were linked to new cases of diabetes. But this association is based on some medical reports. So we hope that looking at hundreds of cases will help us learn more about this relationship,” Rubino said.
Since the coronavirus epidemic began, there have been multiple signs of an unusual rise in type 1 diabetes cases. The number of cases reported by hospitals in northwest London has doubled by the summer of 2020, while a research paper in Nature earlier this year found that coronavirus survivors in the United States are more at risk and more likely to develop diabetes. Six months after infection compared to uninfected people.
Scientists are now trying to prove that the coronavirus is actually directly responsible for the spike in cases. Shuibing Chen, a stem cell scientist at Weill Cornell Medicine, believes there is evidence that the virus can attack beta cells and cause inflammation of the pancreas and other organs, causing damage to various systems that control blood sugar levels.
“We detected viral antigens in human beta cells in autopsy samples from coronavirus patients, which supports the role of direct infection,” Chen said.
But not everyone is convinced. Others have suggested that patients who developed diabetes due to the coronavirus may have already suffered pancreatic damage as a result of intensive steroid treatment during their hospital stay. Or maybe they were in the early stages of developing diabetes, and the coronavirus may have caught the disease again.
“There have been some reports that coronaviruses not only infect beta cells directly, but may also kill them,” said Matthias von Herrath, professor of autoimmunity at the La Jolla Institute of Immunology. But a follow-up report casts doubt on this. idea. “It affects beta cells directly. It affects beta cells in general, so there is no scientific consensus on the accuracy or severity of causing beta cell loss of function.”
In the coming months, we hope that the Coronavirus and Diabetes Registry Database will provide some concrete answers. “We don’t want to be able to answer all the questions, but we do want to learn a lot from these 700 cases that represent perhaps the largest group of virus-related diabetes,” said Rubino. “The coronavirus is the cause of all of these cases. Is there a direct mechanism, if any?” ”
But type 1 diabetes isn’t the only autoimmune disease linked to the coronavirus. Over the past year, numerous reports have indicated a link between the new coronavirus and other autoimmune diseases such as Guillain-Barré syndrome, a rare and serious condition in which the immune system attacks nerves, causing numbness, balance problems, weakness, pain, and sometimes paralysis. .