"The average person with hepatitis C may be less likely to develop cirrhosis or other serious health problems than some researchers have thought previously," lead author Dr. Joshua A. Salomon of the World Health Organization in Cambridge, Massachusetts told Reuters Health.

However, Salomon cautioned that these findings do not mean good news for every individual with hepatitis C virus (HCV). "The news would be better if we could reliably predict which patients will and which will not progress quickly, which is not possible at this time," he noted. As such, doctors must still face the difficult decision of when to put which patients on potentially toxic medications to slow the infection's damage to the liver, Salomon said.

HCV is an infection of the liver that can lead to severe liver diseases such as cirrhosis or cancer. It currently affects around 1.8% of the US population and can be spread via contaminated blood products or by injection drug use.

Salomon explained that it is difficult to understand how liver disease develops because the entire process can last for decades, and many patients are first diagnosed with HCV after they have been infected for some time. He added that many previous estimates of when HCV patients can expect to develop liver disease have been based on patients who have already been diagnosed with liver disease. Patients who come to doctors because they are sick will most likely progress more quickly, the researcher noted, while those with HCV who are healthy enough to remain in the general population may stay disease-free for longer periods.

In the current study, Salomon and his colleagues designed a computer simulation of the US population that could predict when different HCV patients would develop liver disease, then tweaked it until its results matched current data from death registries and national surveys.

Reporting in the recent issue of the American Journal of Epidemiology, the investigators discovered that the model that best matched what is seen in real HCV patients was one in which they had a relatively low rate of developing liver disease.

"Because the disease progresses so slowly in some people, they are likely to reach an old age and die from something else before their hepatitis C infections ever progress to serious liver disease such as cirrhosis or cancer," Salomon explained.

For example, past studies have suggested that people infected with the virus in their 20s might develop cirrhosis anywhere from 20 to 38 years later. The new calculation suggested that half of men infected at age 25 would develop cirrhosis within the next 46 years and that fewer than 30% of women infected at this age "would ever develop cirrhosis," according to the report.

Previous evidence suggests that men, heavy alcohol drinkers, and people infected at an older age may be more likely than others to progress to liver disease from HCV. However, each individual is different, Salomon noted.

"The fact that many infected people will not progress to cirrhosis should be one of several important considerations in individual decisions about whether or not to start treatment, along with the costs, potential side effects, and limited effectiveness of available therapies," he said.