A bad liver can be a potentially fatal problem.

The liver's primary function is to filter out toxic substances from your blood and to produce the essential proteins that allow the body to function.

But liver functions can be damaged or impaired - especially by unhealthy habits like excessive alcohol use, drug use or obesity.

In advance of World Hepatitis Day on July 28, we wanted to learn more about liver disease -- the different types, and how to prevent them and protect yourself and your loved ones – so we spoke with Army Lt. Col. (Dr.) Brendan Graham, chief of pathology at Womack Army Medical Center, in Fort Bragg, North Carolina.

Graham explained there are several varieties of the disease which can be caused by different factors, including:

• Alcoholic Hepatitis (caused by excessive alcohol consumption)
• Viral Hepatitis (caused by infection from viruses that target the liver)
• Drug-induced hepatitis (caused by certain medications like acetaminophen or dietary supplements)
• Steatohepatitis, or fatty-liver disease (caused by being overweight or obese)

All of the hepatitis variants can be very dangerous.

"All viral hepatitis can cause abdominal pain and jaundice - the yellowing of the skin and buildup of bilirubin - in the acute stage," said Graham. "Hepatitis that persists can lead to acute liver failure, which can lead to rapid coma and death as the body loses the capacity to process toxic materials in the blood or produce necessary proteins, or chronic liver failure, where the body gradually loses the ability to process toxins and produce proteins, causing numerous medical complications and leading to eventual death due to liver failure."

Liver failure can be either acute, meaning it is brought on suddenly by a specific event, or it can be chronic, which develops over time.

Graham said that "the types of hepatitis that lead to acute liver failure include drug-induced hepatitis - which can be caused by acetaminophen, also known as Tylenol - and certain types of infectious hepatitis, such as viral hepatitis caused by the hepatitis A virus (HAV)".

Similarly, he said the types of hepatitis that lead to chronic liver failure include alcoholic hepatitis, fatty-liver disease, and certain types of viral hepatitis, such as those caused by the hepatitis B (HBV), and hepatitis C (HCV) viruses.

Knowing the difference is important because it allows individuals to avoid death due to acute liver failure, said Graham. Additionally, most of the types of hepatitis that cause chronic liver failure are due to lifestyle choices, such as excessive alcohol use and obesity, making this type of hepatitis largely avoidable through lifestyle modifications.

"Infectious causes of hepatitis can be transmitted to other individuals by means of blood, sexual contact, and feces," added Graham. "Knowledge of these routes of transmission allow individuals to refrain from activities that could result in transmission or enact lifestyle modifications or public health measures that could reduce the risk or prevent transmission."

Graham added: "The multiple medical complications that come with chronic liver failure secondary to chronic hepatitis require significant medical care, numerous doctor visits, and hospitalizations to treat complications like excessive bleeding and excessive swelling."

It can also affect service members' readiness.

"Service members with chronic liver failure secondary to chronic hepatitis are non-deployable as a result of these complications and the significant medical care they require," he said. "Additionally, service members with viral hepatitis that are not yet in liver failure put their fellow service members at risk of contracting the virus due to exposure to the infected individual's blood in the course of providing medical care to an injured, infected individual or receiving a battlefield blood transfusion from an infected individual."

In the United States, the most common and severe types of viral hepatitis are those caused by HAV, HBV, and HCV.

"Chronic hepatitis leading to liver failure is an almost entirely preventable disease," said Graham. "Maintaining a healthy weight, consuming alcohol in moderation, and avoiding high-risk activities like intravenous drug use and sharing injection needles can prevent the vast majority of chronic hepatitis."

Additionally, he said there are new medical therapies for hepatitis C that can effectively cure the disease. "If an individual is at risk for having contracted hepatitis C, treatment with these drugs early in the course of infection can prevent the chronic liver inflammation that leads to liver failure."

Below is more information on the symptoms and the type of the disease each virus causes:

Symptoms:

• Jaundice
• Fever
• Fatigue
• Loss of appetite
• Nausea
• Vomiting
• Abdominal pain
• Joint pain
• Dark urine
• Clay-colored stool
• Diarrhea (HAV only)

Hepatitis A:

• Transmitted through close person-to-person and sexual contact with an infected person as well as by ingesting contaminated food and/or water.
• Shed through infected feces – people who practice inadequate hygiene can contaminate prepared food with the virus and spread it to others.
• This is the type of viral hepatitis linked to large outbreaks at a single restaurant or in a home.
• Has an incubation period of 15-50 days, with an average of 28 days.

Hepatitis B:

• Primarily transmitted from infected mothers to their babies during childbirth, through sexual contact with an infected individual, and through contact with an infected individual's blood, such as by sharing infected needles, syringes, or other injection-drug equipment.
• Has an incubation period of 60-150 days, with an average of 90 days.

Hepatitis C:

• Primarily transmitted through contact with an infected individual's blood, such as by sharing needles, syringes, and other injection-drug equipment. Also transmissible through sexual contact and from mothers to babies during childbirth.
• Is much less common than the hepatitis B virus.
• For more than half of people who become infected with the hepatitis C virus, it becomes a long-term, chronic infection, which can result in serious, even life-threatening health problems like cirrhosis and liver cancer.
• People with chronic hepatitis C can often have no symptoms and don't feel sick.
• Incubation period of 14-182 days, with an average range of 14-84 days.

For more information, refer to the Centers for Disease Control & Prevention resources and/or talk to your MHS provider.