Prescription drugs (illustrative)
Prescription drugs (illustrative)Flash90

The FDA has now issued a warning that medicines used to treat Hepatitis C may cause flare-ups in patients who suffer from Hepatitis B.

Dr. John Farley, deputy director of FDA's Office of Antimicrobial Products, said, "Doctors should be screening everybody."

In a public statement, the FDA wrote, "We identified 24 casess of hepatitis B reactivation reported to FDA and from the published literature in hepatitis B/ hepatitis C co-infected patients treated with direct-acting antivirals during the 31 months from November 22, 2013 to July 18, 2016. This number includes only cases submitted to FDA, so there are likely additional cases about which we are unaware. Of the cases reported, two patients died and one required a liver transplant."

One issue is that only about half of Hepatitis C patients are actually tested for the virus. The virus is spread mainly by blood contact, including transfusions, infected needles, and mother-to-baby transmission during birth. Though all Hepatitis viruses affect the liver, Hepatitis C is the leading cause of liver transplant.

Hepatitis B has no cure, but like CMV and EBV, it can go "dormant." Though there are drugs to treat Hepatitis B, none can cure it. Hepatitis B is transferred via bodily fluids.

Though there is a vaccine against Hepatitis B, there is not yet a vaccine for Hepatitis C.

It's not clear why Hepatitis C medications would cause a flare-up of Hepatitis B. The first cases of this were noticed about a year ago, and the research has just begun.