DAAs could halt HCV epidemic in US – but only with near-universal testing and big increase in treatment rates

Treatment using direct-acting agents (DAA) could have a major impact on the hepatitis C virus (HCV) epidemic in the United States, according to a model published in online edition of Clinical Infectious Diseases. A four-fold increase in treatment rates could prevent over a quarter of a million HCV-related deaths by 2040, and prevalence could be reduced by 90% with the scaling up of screening efforts, especially the targeting of people who inject drugs (PWID). But the investigators caution that elimination of the epidemic with DAAs would require near-universal testing and a 20% annual treatment rate.

“We found that HCV prevalence, HCV-associated liver disease, and HCV-associated mortality in the United States can be substantially reduced through widespread treatment with DAAs,” write the researchers. “Up to 150,000 additional cases could be identified by increasing HCV screening, effectively eliminating HCV from the noninjecting population. Further opportunities exist to greatly reduce prevalence and new infections among PWIDs through targeted screening and treatment.”

An estimated 5 million individuals in the United States have chronic HCV infection. More than half are unaware of their status, including two-thirds of people who inject drugs who have HCV, the population most affected by HCV.

Glossary

cirrhosis

Severe fibrosis, or scarring of organs. The structure of the organs is altered, and their function diminished. The term cirrhosis is often used in relation to the liver. 

morbidity

Illness.

epidemiology

The study of the causes of a disease, its distribution within a population, and measures for control and prevention. Epidemiology focuses on groups rather than individuals.

cure

To eliminate a disease or a condition in an individual, or to fully restore health. A cure for HIV infection is one of the ultimate long-term goals of research today. It refers to a strategy or strategies that would eliminate HIV from a person’s body, or permanently control the virus and render it unable to cause disease. A ‘sterilising’ cure would completely eliminate the virus. A ‘functional’ cure would suppress HIV viral load, keeping it below the level of detection without the use of ART. The virus would not be eliminated from the body but would be effectively controlled and prevented from causing any illness. 

PWID

Short for people who inject drugs.

DAAs have transformed the treatment of DAAs, achieving cure rates in excess of 90%. They have both individual and public health benefits: reducing rates of liver-related illness and death, and also preventing transmissions.

However, the full benefit of DAAs is likely to be compromised because of low rates of screening and treatment uptake, especially among people who inject drugs.

A team of investigators therefore developed a model to calculate the potential impact of current and enhanced levels of treatment and screening on the HCV epidemic through to 2040.

The model was based on epidemiological data collected between 1992 and 2014. It took into account age-related prevalence and transmission mode. The impact of enhanced screening beyond current populations (a guideline issued in 2012 recommended the routine testing of those born between 1945 and 1965) and also expansion of treatment rates. The investigators also modelled the rates of testing and treatment required to control the epidemic among people who inject drugs.

Approximately 100,000 individuals each year currently access HCV therapy. If this figure remained unchanged, there would be almost 900,000 new infections and over 800,000 HCV-related deaths by 2040. However, overall prevalence would also fall by 80%.

If annual treatment increased to 200,000, 300,000 or 400,000, the 80% reduction would be achieved by 2031, 2028 or 2025, respectively.

Increasing treatment rates would also achieve significant improvements in liver-related illness and death. Doubling rates would prevent approximately 290,000 new cases of cirrhosis and 140,000 liver-related deaths. A four-fold increase would avert over 500,000 new cirrhosis diagnoses and in excess of 250,000 deaths.

Without an expansion of screening, at least 462,000 HCV cases would go untreated. Universal screening of individuals who do not inject drugs was shown to have the potential to reduce prevalence to 300,000 cases. Reducing prevalence below this level would require a targeted offer of testing among people who inject drugs.

Currently, the annual screening rate in this population is a little over 4%. If unchanged, by 2040 total prevalence among people who inject drugs would fall by at most 53% and the annual rate of new infections would fall by no more than 15%. A reduction in prevalence of 90% among people who inject drugs would require annual screening and treatment rates of 20% and 30%, respectively.

“DAAs hold tremendous promise of improving health outcomes and reducing transmissions,” conclude the authors. “Our analysis provides a forecast for the potential impact of DAAs in reducing HCV-associated liver disease, demonstrating that achievable expansion of HCV treatment at current screening rates can substantially reduce morbidity and mortality.”

References

Durham DP et al. The impact of enhanced screening and treatment of hepatitis C in the United States. Clin Infect Dis. Online edition, doi:10.1093/cid/civ894 (2015)