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Hepatitis C Rising -- Especially Among Young People -- and May Be Underestimated

The Centers for Disease Control and Prevention (CDC) Division of Viral Hepatitis has released its 2013 Viral Hepatitis Surveillance Report, providing the latest data on hepatitis A, B, and C in the U.S. While hepatitis C has traditionally been predominant among Baby Boomers, the new report shows that HCV incidence is rising fastest among young people. But a recently published related study suggests that formal surveillance methods may grossly underestimate the number of people newly infected with HCV.

The surveillance report includes figures from 2013 -- the most recent year for which complete data are available -- on acute cases (new infections), prevalence (all existing cases), and related deaths for hepatitis A, B, and C, as reported via the CDC's National Notifiable Diseases Surveillance System (NNDSS).

Hepatitis A is usually spread through contaminated food or water (fecal-oral route) and resolves on its own without treatment. Hepatitis B and C are blood-borne viruses that can become chronic. Over years or decades they can cause serious liver disease including cirrhosis and liver cancer, but they often have no symptoms at early stages. Antiviral treatment can suppress hepatitis B long-term, but usually does not lead to a cure. New interferon-free direct-acting antiviral therapy can cure more than 90% of people with chronic hepatitis C, but it is possible to become infected again. There are effective vaccines for hepatitis A and B, but not yet for C.

Report Highlights

• Hepatitis A

o   Reported cases: 1781

o   Estimated total cases: 3473

o   Related deaths: 80

o   The number of reported hepatitis A cases increased 14% from 2012 to 2013, in part due to an outbreak related to pomegranate seeds.

• Hepatitis B

o   Reported acute cases: 3050

o   Estimated total new cases: 19,764

o   Estimated chronic cases: 700,000 - 1.4 million

o   Related deaths: 1873

o   Reported cases of acute hepatitis B rose 5.4% from 2012 to 2013 -- the first increase since 1990.

• Hepatitis C

o   Reported acute cases: 2138

o   Estimated total new cases: 29,718

o   Reported past (cleared) or present cases: 132,452

o   Estimated chronic cases: 3.2 million

o   Related deaths: 19,368

o   Reported cases of acute hepatitis C increased by 152% from 2010 to 2013, with the largest increase among young adults age 20-29.

o   Most cases of reported past or present hepatitis C were among people age 40 or younger.

o   Hepatitis C-related deaths increased from 2009 to 2013, with the highest mortality rate among adults age 55-64.

The report authors stressed that these data have limitations because not all cases of viral hepatitis are identified or reported to state health departments that share data with the CDC. To overcome these limitations, the CDC "would like to strengthen viral hepatitis surveillance efforts in the U.S., improve state and local capacity to detect new infections, coordinate prevention activities, provide feedback to providers for quality improvement, and track progress toward prevention goals."

"These steps coupled with enhanced targeted prevention programs in states reporting the largest increases in new hepatitis C cases would result in tremendous strides in reducing the toll of viral hepatitis in this country as well as progress toward achieving the goals of the national Viral Hepatitis Action Plan," they wrote. "These and other efforts can control and prevent continued transmission of viral hepatitis infections, viral hepatitis-related illnesses, and deaths."

The full CDC surveillance report is available for free online

Underascertainment of Hepatitis C

As described in the June 30 advance edition of the Annals of Internal Medicine, Shauna Onofrey from the Massachusetts Department of Public Health and colleagues aimed to validate estimates of acute HCV incidence by determining how many clinical diagnoses were reported to the Massachusetts Department of Public Health (DPH) and the CDC.

Onofrey's team worked with older hepatitis C incidence data from 2010. As stated in the most recent report discussed above, cases of acute HCV infection rose from 850 in 2010 to 1229 in 2011 to 1778 in 2012 and finally to 2138 in 2013. Based on the 850 reported cases, the CDC estimated there were about 17,000 total new cases in 2010.

This case series and chart review analyzed information from 183 patients clinically diagnosed with acute hepatitis C between 2001 and 2011 who participated in a research study. They received care at 2 hospitals and the state correctional health care system in Massachusetts. The researchers looked at data including HCV antibody test results, ALT liver enzyme levels, and symptoms of acute infection.

Of these 183 clinical cases of acute HCV infection, 149 (81%) were reported to the Massachusetts DPH for surveillance classification. The DPH investigated 43 of these reports as potential acute cases based on their surveillance criteria, and ultimately only 1 case met the national case definition and was counted in the CDC's nationwide statistics.

Discordance between clinical and surveillance classification was often related to missing clinical or laboratory data at the DPH, as well as restrictive definitions such as requiring negative hepatitis A and B laboratory results to rule out other potential causes for ALT elevations or symptoms.

"Clinical diagnoses of acute HCV infection were grossly underascertained by formal surveillance reporting," the study authors summarized. "This investigation showed that fewer than 1% of clinically diagnosed acute cases of HCV infection between 2001 and 2011 in Massachusetts ultimately were reported to the CDC as confirmed acute surveillance cases of HCV infection and included in national estimates of incidence of HCV infection."

"Incomplete clinician reporting, problematic case definitions, limitations of diagnostic testing, and imperfect data capture remain major limitations to accurate case ascertainment despite automated electronic laboratory reporting," they continued. The primary reason was not clinicians failing to report to the DPH, because approximately 80% of acute cases were reported and eligible for further investigation by the state.

The researchers said they agree with the CDC's decision to add antibody seroconversion to the surveillance case definition of acute HCV infection in late 2012, which helps account for new cases without symptomatic illness and removes the need for negative hepatitis A and B tests. But use of seroconversion criteria necessitates regular testing to determine when results change from negative to positive.

"Our analysis suggests that national incidence of HCV infection during this time frame may be greater than previously estimated," they concluded. "In the context of a staggering increase in opiate use, with estimates of new heroin injectors reaching 178,000 in 2011 and related outbreaks of HCV infection in other geographic locations, a reexamination of the methods for measuring the burden of incident HCV infection in the United States is necessary."

7/3/15

References

Centers for Disease Control and Prevention Division of Viral Hepatitis. Surveillance for Viral Hepatitis -- United States, 2013. May 31, 2015.

S Onofrey, J Aneja, GA Haney, et al. Underascertainment of Acute Hepatitis C Virus Infections in the U.S. Surveillance System: A Case Series and Chart Review. Annals of Internal Medicine. June 30, 2015 (Epub ahead of print).