The Petri Dish: Hepatitis C: another baby boomer legacy
March 7, 2013
We hear a lot about the baby boomers, from their influence on popular culture to their economic impact on our federal retirement and medical systems. Perhaps less well known is that the baby boomer generation is also associated with a very unusual blood-borne virus that causes hepatitis. The hepatitis C virus targets the liver and establishes a life-long chronic infection that is largely asymptomatic but can progress to chronic hepatitis, cirrhosis (liver scarring) and eventually liver cancer. Surprisingly, 75 percent of hepatitis C-infected individuals in the U.S. are baby boomers.
So why is the hepatitis C virus linked to the baby boomer generation? The answer is that, unlike most other pathogens, the virus is not usually transmitted from person to person by traditional routes – sneezing, bodily contact, sex or a vector (such as a mosquito). Rather, the virus is primarily transmitted by invasive procedures, such as blood transfusion, organ transplant, the handling of blood products, the use of dirty needles among drug addicts and being born to a hepatitis C virus-infected mother. While the virus can also be transmitted through sexual intercourse, such transmissions appear to be relatively rare. Thus, unlike most other pathogens, the survival of the virus is primarily dependent on invasive human intervention. The virus was able to thrive in the U.S. in the ’60s, ’70s and ’80s because we were unaware of its presence until 1988. Therefore, drug users and blood or organ transplant recipients were prime targets for the virus. In addition, because most infections are relatively symptom-free with the major impact only developing later in life, there was no reason to be aware of it.
Hepatitis C continues to be a major problem for health authorities worldwide. The World Health Organization reports that about 150 million people are chronically infected with hepatitis C virus and that more than 350,000 people die every year from hepatitis C-related liver diseases. Many patients need liver transplants to survive. However, today we know a lot about the virus and can eliminate it from the blood supply and screen for its presence in organ donors via a diagnostic test. Consequently, the incidence of hepatitis C has dropped dramatically in the U.S. over recent decades; the number of new infections has declined from 230,000 per year in the 1980s to approximately 17,000 in 2010. In the past it was not generally recommended that healthy individuals be tested, since no effective treatment or cure was available. But in recent years there have been significant advances in the treatment of hepatitis C, and it is now possible to cure many, though not all, cases of infection. Last year, the U.S. Centers for Disease Control began to recommend for the first time that all Americans born between 1945 and 1965 be tested for the virus. There is now hope that the virus can be eliminated in the U.S.
So where did this virus come from? It is hard to imagine that a virus dependent on invasive human intervention could ever evolve. The most likely answer is that the virus is primarily an animal virus that jumped into the human population. One possibility is that, like the human immunodeficiency virus, it originated in non-human primates prior to infecting humans. Indeed, viruses related to hepatitis C have been found in primates. And a new virus related to the hepatitis C virus has recently been discovered in bats in Bangladesh, suggesting that bats may serve as the primary reservoir for this class of viruses. Under normal circumstances, the transmission of the virus from a bat to a human would be a dead end since the virus could not be transmitted further. But the development of various practices that allowed blood to be directly transferred between humans provided a mechanism for the virus to cause a global epidemic.
Unlike for hepatitis A and B, which are primarily transmitted through food and sexual contact, respectively, there is currently no available vaccine to prevent contraction of hepatitis C. But the good news is that we can control this virus through appropriate screening, education and the availability of curative treatments. If caught early enough, interferon treatments that boost the immune system can contain and often eliminate the virus. And safer practices will hopefully help make it extinct altogether – a distant memory of another age.
David L. “Woody” Woodland, Ph.D. is the Chief Scientific Officer of Silverthorne-based Keystone Symposia on Molecular and Cellular Biology, a nonprofit dedicated to accelerating life science discovery by convening internationally renowned research conferences in Summit County and worldwide. Woody can be reached at (970) 262-1230 ext. 131 or firstname.lastname@example.org.