Hepatitis E

Causative agent

Hepatitis E is a liver disease caused by the hepatitis E virus (HEV). All HEV reported to infect humans belong to the Orthohepevirus genus. The Orthohepevirus genus is classified into four species, HEV-A to HEV-D, which circulate in different hosts. While the usual HEV causing human infection belongs to HEV-A, cases of human infection with HEV-C (also known as rat HEV) have rarely been reported, especially in immunosuppressed people.

Clinical features

Clinical features of acute hepatitis E are similar to those of other types of viral hepatitis. Typical signs and symptoms of hepatitis E include:

• An initial phase of fever, reduced appetite, nausea and vomiting, lasting for a few days;
• Abdominal pain, itching, skin rash, or joint pain;
• Jaundice (yellow discolouration of the skin and sclera of the eyes, with dark urine and pale stools); and
• A slightly enlarged, tender liver (hepatomegaly).

These symptoms are often indistinguishable from those experienced during other hepatic illnesses and typically last for 1 - 6 weeks.

In rare cases, acute hepatitis E can result in fulminant hepatitis (acute liver failure) and death. Fulminant hepatitis occurs more frequently when hepatitis E occurs during pregnancy. Pregnant women with hepatitis E are at an increased risk of acute liver failure, fetal loss and mortality. Case fatality rates as high as 20 - 25 % have been reported among pregnant women in their third trimester. Other high-risk individuals such as elderly with major underlying illnesses, transplant patients, as well as people with chronic liver diseases and glucose-6-phosphate dehydrogenase (G6PD) deficiency may also develop severe illness when having HEV infection.

Cases of chronic hepatitis E infection have been reported in immunosuppressed people.

Mode of transmission

The usual HEV causing human infection is transmitted mainly through the faecal-oral route, for example, due to faecal contamination of drinking water. Besides, foodborne transmission can result from ingestion of undercooked meat or meat products produced from infected animals (HEV has been detected in pig livers). Other rare transmission routes identified include:

• Transfusion of infected blood products;
• Organ transplant; and
• Vertical transmission from a pregnant woman to her foetus.

Hepatitis E outbreaks usually follow periods of faecal contamination of drinking water supplies and may affect several hundred to several thousand persons. The ingestion of raw or undercooked shellfish may be the source of sporadic cases in endemic areas.

The infected persons are believed to excrete the virus beginning a few days before to around 3 - 4 weeks after the onset of disease.

For human infection with rat HEV, the exact mode of transmission is unknown at the moment. Possible routes of transmission include:

• Ingestion of food or water contaminated by rodents or their excreta;
• Exposure to environments or objects contaminated by rodents or their excreta; and
• Direct contact with rodents or their excreta.

Incubation period

The incubation period following exposure to the usual HEV causing human infection ranges from 2 - 10 weeks, with a mean of 5 - 6 weeks. The incubation period of human infection with rat HEV is unknown at the moment.

Management

There is no specific treatment capable of altering the course of acute hepatitis E. Prevention is the most effective approach against the disease. As hepatitis E is usually self-limiting, hospitalisation is generally not required. However, hospitalisation is required for people with fulminant hepatitis and should also be considered for symptomatic pregnant women.

Prevention

At the population level, the risk of hepatitis E infection and transmission can be reduced by:

• Maintaining quality standards for public water supplies.
• Establishing proper disposal systems to eliminate sanitary waste.

1. Maintain good personal hygiene

• Perform hand hygiene frequently, wash hands thoroughly especially before handling food or eating, and after using the toilet or handling vomitus or faecal matter. Wash hands with liquid soap and water, and rub for at least 20 seconds. Then rinse with water and dry with a disposable paper towel or hand dryer. If hand washing facilities are not available, or when hands are not visibly soiled, hand hygiene with 70 to 80% alcohol-based handrub is an effective alternative.
• Wear gloves and a mask while disposing of or handling vomitus and faeces, and wash hands thoroughly afterwards.
• Use serving chopsticks and spoons at meal time. Do not share food and drinks with others.
• Refrain from work or school, and seek medical advice when suffering from vomiting or diarrhoea.
• Exclude infected persons and asymptomatic carriers from handling food and from providing care to children, elderly and immunocompromised persons.

2. Maintain good food hygiene

• Adopt the 5 Keys to Food Safety in handling food, i.e. Choose (Choose safe raw materials); Clean (Keep hands and utensils clean); Separate (Separate raw and cooked food); Cook (Cook thoroughly); and Safe Temperature (Keep food at safe temperature) to prevent foodborne diseases.
• Drink only boiled water from the mains or bottled drinks from reliable sources.
• Avoid drinks with ice of unknown origin.
• Purchase fresh food from hygienic and reliable sources. Do not patronize illegal hawkers.
• Clean and wash food thoroughly. Cook food, especially seafood (e.g. shellfish), pork and pig offal, thoroughly before consumption. Avoid raw food or undercooked food.
• Store food properly or in the refrigerator, do not place food at ambient temperature for a long time.
• Slice raw meat and offal into thin strips to allow thorough cooking, especially during hotpot or congee cooking.
• Cook the shellfish and offal (such as pig liver) in boiling water for a relatively long period of time, say three to five minutes, to ensure that it is thoroughly cooked.
• For meat and offal, make sure that juices are clear, not red, blood is not visible when you cut the cooked meat and offal.
• When having hotpot, use separate chopsticks and utensils for handling raw and cooked foods to prevent cross-contamination.

* Please visit the website of Centre for Food Safety for more information on food safety.

3. Maintain good environmental hygiene

Use 1:99 diluted household bleach for general household cleaning and disinfection as household detergent may not be able to kill HEV.

In general, rodents (such as rats) can transmit multiple diseases to humans directly and indirectly. The public are advised to adopt the following measures: 

• Eliminate sources of food and nesting places for rodents in living environment. Store food in covered containers and handle pet food properly to avoid it becoming food for rodents;
• Store all refuse and food remnants in dustbins with well-fitted cover. Dustbins must be emptied at least once a day;
• Keep premises, especially refuse rooms and stairways clean. Avoid accumulation of articles;
• Inspect all flowerbeds and pavements for rodent infestation regularly; and
• Avoid high risk activities below to reduce rodent contact:
• Avoid rodent contact and places dirtied with rodent excreta;
• Avoid handling rodents with bare hands;
• Wash hands with liquid soap and water immediately after handling animals, and disinfect contaminated areas; and
• If wound appears, clean broken skin immediately and cover it properly with waterproof adhesive dressings.