Parkinson’s disease is not contagious and cannot be passed from one person to another. Parkinson’s happens when the brain cells (neurons) responsible for making dopamine begin to break down and die.

Doctors do not yet know why some people are more susceptible to Parkinson’s than others.

There is a group of disorders that closely resemble Parkinson’s disease. Because they share many of the same symptoms as Parkinson’s disease, they are collectively known as Parkinsonisms.

Researchers have been investigating whether Parkinson’s disease and Parkinsonisms could be triggered by viral infections in certain predisposed people.

Parkinson’s disease is a degenerative brain disease, which means it happens when brain cells begin to die. It is typically age-related and affects about 1 percent of people over the age of 60.

Parkinson’s disease typically progresses slowly over the course of many years.

Symptoms of Parkinson’s disease can include:

  • tremors
  • slowed movements
  • stiff, rigid muscles that make movement difficult
  • changes in walking (shuffling, small steps)
  • balance and coordination difficulties
  • speech changes (soft speech, monotone speech)
  • posture changes
  • trouble with thinking and memory, which is more common in late-stage and atypical Parkinson’s

Parkinsonism is an umbrella term used to describe the symptoms of Parkinson’s disease. The term refers to both Parkinson’s disease and conditions that cause similar symptoms.

Several neurological conditions and physical ailments can cause symptoms that resemble Parkinson’s disease. Some of these conditions may be labeled atypical Parkinson’s diseases.

Parkinsonisms tend to progress more quickly than Parkinson’s disease. They also tend to include additional symptoms not commonly found in Parkinson’s disease.

Examples of neurodegenerative Parkinsonisms include multiple system atrophy and corticobasal degeneration.

Doctors don’t know exactly why Parkinson’s disease affects certain people. Researchers currently think there are multiple factors at play, including a combination of genetics and environmental factors.

About 10 percent of people with Parkinson’s disease have a family history of the condition. But most people have what’s known as idiopathic Parkinson’s disease. Idiopathic is a term doctors use to describe conditions with no known causes.

What else causes Parkinson’s-like symptoms?

  • medications
  • repeated head trauma
  • degenerative brain disorders
  • brain tumors or lesions
  • exposure to toxins
  • post-infectious encephalitis
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Although doctors do not know exactly what causes Parkinson’s disease, they do have a good idea of what’s happening inside the brain when someone has the condition.

A part of the brain called the basal ganglia houses neurons that produce dopamine. Dopamine is a neurotransmitter (chemical messenger) responsible for many functions in the body, like the smooth movement of muscles.

In people with Parkinson’s disease, dopamine-producing neurons die or become impaired in their function. As a result, there is less dopamine available in the brain.

Another neurotransmitter called norepinephrine may also be affected in people with Parkinson’s disease. This is a neurotransmitter that controls heart rate, blood pressure, and other bodily functions.

Some severe viral and bacterial infections lead to encephalitis, which is a dangerous condition that causes inflammation in the brain. Encephalitis can cause Parkinson-like symptoms. This has led researchers to explore the connections between viral infections and Parkinsonism.

To date, this research has been limited. It’s possible that infections play a role in the development of Parkinson’s disease, but researchers have yet to find any clear connections.

Viruses being investigated include:

To be clear, getting one of these viruses does not mean that you will get Parkinson’s disease. Researchers are trying to determine if infectious illnesses may change something in a person’s body that makes them more vulnerable to the condition.

Researchers are trying to see if there are connections between illnesses in earlier life and increased risks for Parkinson’s disease.

According to a 2019 review of studies, there is some evidence suggesting that:

  • People who get the flu vaccination may be less likely to get Parkinson’s disease than people who don’t.
  • People with higher levels of the herpes simplex virus in their bodies may have more severe Parkinson’s disease symptoms.
  • People with Parkinson’s are more likely to have had the Epstein-Barr virus than the general population.
  • People with a history of hepatitis C may be more likely to get Parkinson’s disease than others.

There are several risk factors for Parkinson’s disease that are more clearly understood. These known risk factors have stronger supporting evidence than the infection-related risk factors discussed above.

Risk factors for Parkinson’s disease include:

  • Sex. Parkinson’s disease is more common in men who were assigned male at birth.
  • Age. Parkinson’s disease is much more common in older adults, and the risk increases with age. Young people rarely get Parkinson’s, but the condition can begin developing years before symptoms appear.
  • Genetics. Parkinson’s disease is more common in people who have several relatives with the condition.
  • Toxins. People exposed to pesticides and other toxins may be at an increased risk.

No single test exists to diagnose Parkinson’s disease. Doctors rely on a physical examination and your symptom history to help make a diagnosis. They will look specifically for motor-related symptoms, such as how you walk.

Your doctor may run some tests to rule out other potential causes of your symptoms, like stroke. Tests could include imaging tests, blood tests, and more. Doctors may even prescribe Parkinson’s disease medications to see if a person’s symptoms improve.

If a person has a considerable family history of Parkinson’s disease, it’s possible that doctors may be able to conduct genetic testing. But this is costly and uncommon.

Parkinson’s disease is a progressive disorder with currently unknown causes. Researchers are continuing to make connections between potential underlying causes with the hopes of one day preventing the disease from developing altogether.