Exposure to the hepatitis A virus can cause an acute infection of the liver that is typically mild and resolves on its own. The symptoms and duration of illness vary a great deal, with many persons showing no symptoms at all. Fever and jaundice are two of the symptoms most associated with a hepatitis A infection.
The Incidence of Hepatitis A Infections
Hepatitis A is much more common in countries with underdeveloped sanitation systems and, thus, is a risk in most of the world. An increased transmission rate is seen in all countries other than the United States, Canada, Japan, Australia, New Zealand, and the countries of Western Europe. Nevertheless, infections continue to occur in the United States, where approximately one-third of the population has been previously infected with HAV.
Each year, approximately 30,000 to 50,000 cases of hepatitis A occur in the United States. Historically, acute hepatitis A rates have varied cyclically, with nationwide increases every 10 to 15 years. The national rate of HAV infections has declined steadily since the last peak in 1995. Although the national incidence—1.0 cases per 100,000 population—of hepatitis A was the lowest ever recorded in 2007, it is estimated that asymptomatic infections and underreporting kept the documented incidence-rate lower than it is. In fact, it is estimated that there were 25,000 new infections in 2007.
How is Hepatitis A transmitted?
Hepatitis A is a communicable (or contagious) disease that often spreads from person to person. Person-to-person transmission occurs via the “fecal-oral route,” while all other exposure is generally attributable to contaminated food or water. Food-related outbreaks are usually associated with contamination of food during preparation by a HAV-infected food handler. The food handler is generally not ill because the peak time of infectivity—that is, when the most virus is present in the stool of an infected individual—occurs two weeks before illness begins.
Fresh produce contaminated during cultivation, harvesting, processing, and distribution has also been a source of hepatitis A. In 1997, frozen strawberries were the source of a hepatitis A outbreak in five states. Six years later, in 2003, fresh green onions were identified as the source of a hepatitis A outbreak traced to consumption of food at a Pennsylvania restaurant. Other produce, such as blueberries and lettuce, has been associated with hepatitis A outbreaks in the U.S. as well as other developed countries.
HAV is relatively stable and can survive for several hours on fingertips and hands and up to two months on dry surfaces. The virus can be inactivated by heating to 185°F (85°C) or higher for one minute or disinfecting surfaces with a 1:100 dilution of sodium hypochlorite (household bleach) in tap water. It must be noted, however, that HAV can still be spread from cooked food if it is contaminated after cooking.
Although ingestion of contaminated food is a common means of spread for hepatitis A, it may also be spread by household contact among families or roommates, sexual contact, or by direct inoculation from persons sharing illicit drugs. Children are often asymptomatic, or have unrecognized infections, and can pass the virus through ordinary play, unknown to their parents, who may later become infected from contact with their children.
Symptoms of Hepatitis A Infection
Hepatitis A may cause no symptoms at all when it is contracted, especially in children. Asymptomatic individuals will only know they were infected (and have become immune, given that you can only get hepatitis A once) by getting a blood test later in life. Approximately 10 to 12 days after exposure, HAV is present in blood and is excreted via the biliary system into the feces. Although the virus is present in the blood, its concentration is much higher in feces. HAV excretion begins to decline at the onset of clinical illness and decreases significantly by 7 to 10 days after onset of symptoms. Most infected persons no longer excrete virus in the feces by the third week of illness; children may excrete HAV longer than adults.
Seventy percent of hepatitis A infections in children younger than six years of age are asymptomatic; in older children and adults, infection tends to be symptomatic with more than 70% of those infected developing jaundice. Symptoms typically begin about 28 days after contracting HAV but can begin as early as 15 days or as late as 50 days after exposure. The symptoms include muscle aches, headache, anorexia (loss of appetite), abdominal discomfort, fever, and malaise.
After a few days of typical symptoms, jaundice (also termed “icterus”) sets in. Jaundice is a yellowing of the skin, eyes and mucous membranes that occurs because bile flows poorly through the liver and backs up into the blood. The urine will also turn dark with bile and the stool light or clay-colored from lack of bile. When jaundice sets in, initial symptoms such as fever and headache begin to subside.
In general, symptoms usually last less than 2 months, although 10% to 15% of symptomatic persons have prolonged or relapsing disease for up to 6 months. It is not unusual, however, for blood tests to remain abnormal for six months or more. The jaundice so commonly associated with hepatitis A can also linger for a prolonged period in some infected persons—sometimes as long as eight months or more. Additionally, pruritus, or severe “itchiness” of the skin, can persist for several months after the onset of symptoms. These conditions are frequently accompanied by diarrhea, anorexia, and fatigue. Relapse is possible with hepatitis A, typically within three months of the initial onset of symptoms. Although relapse is more common in children, it does occur with some regularity in adults. Most persons who are infected with hepatitis A fully recover, and do not develop chronic hepatitis. Persons do not carry hepatitis A long-term as with hepatitis B and C.
Fulminant Hepatitis A
Fulminant hepatitis A is a rare but devastating complication of HAV infection. As many as 50% of individuals with acute liver failure may die or require emergency liver transplantation. Elderly patients and patients with chronic liver disease are at higher risk for fulminant hepatitis A. In parallel with a declining incidence of acute HAV infection in the general population, however, the incidence of fulminant HAV appears to be decreasing.
HAV infects the liver’s parenchymal cells (internal liver cells). Once a cell has been penetrated by the viral particles, the hepatitis A virus releases its own toxins that cause, in essence, a hostile takeover of the host’s cellular system. The cell then produces new viral components that are released into the bile capillaries or tubes that run between the liver’s parenchymal cells. This process results in the death of liver cells, called hepatic necrosis.
The fulminant form of hepatitis occurs when this necrotic process kills so many liver cells—upwards of three-quarters of the liver’s total cell count—that the liver can no longer perform its job. Aside from the loss of liver function, fulminant hepatic failure can lead to encephalopathy and cerebral edema. Encephalopathy is a brain disorder that causes central nervous system depression and abnormal neuromuscular function. Cerebral edema is a swelling of the brain that can result in dangerous intracranial pressure. Intracranial hypertensions leading to brain stem death and sepsis with multiple organ failure are the leading causes of death in individuals with fulminant hepatic failure.
Treatment for Acute Hepatitis A Infection
Once a clinical infection is established, there is no specific treatment for hepatitis A. Affected individuals generally suffer from loss of appetite, so the main concern is ensuring a patient receives adequate nutrition and avoids permanent liver damage. An individual’s perception of the severity of fatigue or malaise is the best determinant of the need for rest.
Treatment of those suffering from fulminant hepatic failure depends largely on the affected person’s status. Those who have not become encephalopathic generally undergo an intense course of supportive treatment. But for those whose liver failure is so complete that it has led to encephalopathy or cerebral edema, timely liver transplantation is often the only option. Unfortunately, many individuals with irreversible liver failure do not receive a transplant because of contraindications or the unavailability of donor livers.
How to Prevent Hepatitis A Infection
Hepatitis A is totally and completely preventable. Although outbreaks continue to occur in the United States, no one should ever get infected if preventive measures are taken. For example, food handlers must always wash their hands with soap and water after using the bathroom, changing a diaper, and certainly before preparing food. Food handlers should always wear gloves when handling or preparing ready-to-eat foods, although gloves are not a substitute for good hand washing. Ill food-handlers should be excluded from work.