Aside from liver cirrhosis or liver cancer, it turns out that hepatitis C infection can lead to other chronic medical issues, including Parkinson’s disease. A new study published in Neurology finds that the hepatitis C virus can lead to an increased risk of Parkinson’s disease, the second most common degenerative brain disorder following Alzheimer’s.

According to the World Health Organization (WHO), up to 150 million people around the world have chronic hepatitis C infection. Hepatitis C is a bloodborne virus that is usually transmitted at birth from infected mothers through sharing needles, or unmonitored blood transfusions. These days, in the U.S., donated blood is screened. But in other parts of the world, it’s less likely to be, posing a risk to anyone who receives a blood transfusion.

The infection can be cured, but it depends on the person; some people will ultimately develop fatal liver conditions because of it. Today, however, several therapies and new antiviral drugs have proven effective in treating and sometimes curing the infection.

“Many factors clearly play a role in the development of Parkinson’s disease, including environmental factors,” said Dr. Chia-Hung Kao of the China Medical University in Taichung, Taiwan, in the press release. “This nationwide study, using the National Health Insurance Research Database of Taiwan, suggests that hepatitis caused specifically by the hepatitis C virus may increase the risk of developing the disease. More research is needed to investigate this link.”

For the study, the researchers examined 49,967 people with some form of hepatitis (placed into a hepatitis B, hepatitis C, or both virus groups) and 199,868 without the disease. Most of the hepatitis patients (71 percent) had hepatitis B while 21 percent had hepatitis C.

The researchers gathered data on the participants for 12 years, tracking whether they developed Parkinson’s disease. They controlled for factors like age, sex, diabetes, and cirrhosis, and still found that people with hepatitis C were 30 percent more likely to get Parkinson’s disease than the people who didn’t have hepatitis.

The researchers didn’t explain why they believe hepatitis C may increase the risk of Parkinson’s, and more research will be needed to fully understand the biological mechanisms. But past research has examined the same link, and found that hepatitis C may enter the central nervous system and contribute to the overexpression of inflammatory biomarkers that’s seen in Parkinson’s disease.

Fortunately for people with hepatitis C, improvements in detection, drugs, and therapies is making it easier for patients to recover and prevent some of the long-term complications of the infection, such as liver damage or Parkinson’s.

Source: Kao C, et al. Neurology, 2015.