What is the epidemiology for hepatitis C?

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The Centers for Disease Control and Prevention (CDC) state that epidemiology is the systematic, scientific review of the causes, risk factors, and distribution of disease and other health-related conditions within well-defined populations.

It examines all potential factors that play into the absence or presence of disease.

So, hepatitis C epidemiology is the study of the determinants and distribution of HCV.

The number of new infections that develops in a region within a defined period represents the incidence of HCV infection. More specifically, the CDC define HCV incidence as the number of acute HCV infections reported per year.

According to Hepatitis C Online, HCV incidence has increased in recent years, and the disease has become a major public health concern.

The CDC’s HCV Surveillance Report notes that the number of acute HCV cases peaked in 1989, then steadily declined until 2010.

In the United States, the estimated number of infections grew from 11,800 in 2010 to 57,500 in 2019, an increase of 387%. Approximately 2.4 million people in the U.S. were HCV RNA positive from 2013 to 2016.

One study indicates that the documented U.S. cases of HCV infection in 2010 were just one-fifth of the people who died from HCV-related disease in the country that year.

HCV prevalence is the percentage of people in a defined population living with active HCV. In the U.S., HCV prevalence rates are subject to the number of:

• newly reported HCV infections
• people who rid their bodies of HCV infection without treatment
• cures with treatment
• reinfections
• deaths

In the U.S.

In 2019, the number of reported acute HCV cases was highest in the following states:

Combined, the cases in these states accounted for around 42% of all reported acute cases within the U.S.

States with the highest rates of reported acute HCV cases in 2019 include:

• Indiana
• West Virginia
• Utah
• South Dakota
• Maine

Other parts of the world

HCV affects an estimated 185 million people in the world. Its prevalence is around 1–2% in developed countries.

Approximately 71 million people globally have chronic HCV infections that put them at risk for liver disease, including liver cirrhosis and liver cancer. These HCV infections lead to 399,000 deaths per year.

HCV prevalence per region is as follows:

Based on sex

In the U.S., males accounted for 60% of acute HCV infections in 2019. Doctors diagnosed acute HCV infections in 2,471 males, compared with 1,653 females.

That same year, HCV prevalence was 1.31% for adult males and 0.57% for adult females. These percentages represent an HCV prevalence ratio of 2.3.

Based on age group

The reported number and rate of acute HCV infections in 2019 were:

• highest in people aged 30–39 years
• second highest in people aged 20–29 years
• lowest in people aged 0–19 years

HCV prevalence in the U.S. is highest in those born between 1945 and 1969, at 1.63%, and second highest in those born after 1965, at 0.51%. Injection drug use is the most common and important risk factor for acquiring HCV in the U.S.

Based on race and ethnicity

In 2019, American Indian and Alaska Native people accounted for the highest rate of acute HCV cases. White people had the second-highest rate, followed by Black non-Hispanic people. White people had the highest number of cases, accounting for 65% of the total.

American Indian and Alaska Native people experienced a dramatic increase in reported acute HCV cases between 2010 and 2019. White people also experienced a steady increase during this time.

There are seven different HCV genotypes, which are strains of the HCV virus. Doctors categorize these HCV genotypes as genotype 1 through genotype 7. A simple blood test can determine the virus genotype.

Genotype 1 is the most prevalent worldwide, and genotype 3 is the second most common.

In the U.S., genotypes 1, 2, and 3 are the most common, with genotype 1 accounting for 60–70% of infections.

A breakdown of genotype prevalence according to geographic regions around the world is as follows:

• genotype 1, which is most widely dispersed worldwide
• genotype 2, which is most prevalent in Central and West Africa
• genotype 3, which is most prevalent in Asia
• genotype 4, which is most prevalent in North Africa and the Middle East
• genotype 5, which is most prevalent in South Africa
• genotype 6, which is most prevalent in Southeast Asia
• genotype 7, which is most prevalent in Central Africa

Countries do not always record deaths due to liver conditions that are associated with HCV as being caused by HCV, even when the virus causes the chronic condition that ends with a loss of life. This is most likely because many years pass between the onset of infection and the time of death.

In the U.S., the CDC uses data from death certificates to report HCV-related mortality. This data likely underrepresents the actual number of deaths caused by HCV.

HCV-related deaths reported in the U.S. peaked in 2014 and 2015 and then declined from 2016 to 2019. About 72% of these reported HCV-related deaths occurred in males and 28% in females.

U.S. death certificates listed hepatitis C as an underlying cause of 15,713 deaths in 2018.

Most people contract HCV through parenteral exposures to infectious blood or body fluids.

Any person could contract HCV, which may lead to the development of hepatitis and chronic liver disease. However, certain individuals have a heightened risk of infection. These include:

• people who use or have used injection drugs
• people who use or have used non-injection drugs
• people receiving hemodialysis
• people who have received blood transfusions, clotting factor concentrates, or organ transplants
• people who have unprotected sexual intercourse
• people who have nonsexual household contact with a person with an HCV infection by sharing toothbrushes, razors, or similar items
• people with HIV
• people who get tattoos or piercings
• healthcare, emergency medical, and public safety workers
• children born to mothers who test positive for HCV

Today, blood banks use more advanced HCV screening tests, reducing the possibility of transmission to those who receive blood transfusions. Before blood screening became available in 1992, blood transfusion was a common cause of HCV infection.

Though unlikely, HCV can spread in healthcare settings when people use equipment such as syringes on multiple patients or injectable medications somehow come into contact with blood.

HVC infrequently spreads in household settings but can result from exposure to the blood of a household member with the infection.

To prevent the spread of HCV, people should:

• avoid sharing needles for injection drug use
• avoid having unprotected sexual intercourse
• avoid sharing toothbrushes, razors, or similar self-care items
• wear protective gear in healthcare settings

Hepatitis C is an increasingly common and potentially fatal liver disease caused by the hepatitis C virus. Various forms of viral hepatitis cause approximately 1.4 million deaths each year. Research links HCV and HBV to 90% of these fatalities.

In recent years, HCV has become a major public health concern in the U.S. as the incidence of the infection has climbed sharply.