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Hepatitis E (HEV)

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by Emma Patten

Hepatitis A is a liver-infecting virus that can be spread in fecally contaminated food and water. Symptoms include nausea, vomiting and sometimes jaundice, a yellowing of the skin due to reduced liver function

The number of cases of hepatitis A may be as high as 60,000 to 140,000 cases per year, two to five times higher than the number of cases reported, estimate Dr. Gregory L Armstrong and colleagues from the National Center for Infectious Diseases, Centers for Disease Control and Prevention (CDC) in Atlanta.

Armstrong and his colleagues came to this conclusion after looking at data from two large nationwide studies and the National Notifiable Diseases Surveillance System (NNDSS), which include data on the number of people with hepatitis A antibody in their blood (a sign of past infection). They then developed a mathematical model to compute an estimated incidence of hepatitis A.

The researchers estimate that the overall incidence of hepatitis A infection has declined by 4.4% per year during this century. Approximately 35% to 65% of cases occur in children between the ages of 0 to 4 years. Data from the National Notifiable Disease Surveillance System indicates that only 1.4% to 1.8% of cases occurring in this age group are reported to the CDC.

Armstrong told Reuters Health that he thinks the disparity in the actual numbers and numbers of cases reported are due to the fact that most children do not show signs of jaundice when infected with hepatitis A. Furthermore, he said, physicians may not always report cases of hepatitis A infection to the CDC.

Hepatitis A - Clinical Features

Notes:
The average incubation period for hepatitis A is 30 days with a range of 15 to 45 days. The severity of clinical disease associated with HAV infection increases with increasing age; icteric disease occurs among <10% of children younger than 6 years of age, 40%-50% of older children, and 70%-80% of adults. Complications of hepatitis A include fulminant hepatitis in which the case fatality rate can be >50% despite modern medical interventions such as liver transplantation, cholestatic hepatitis with very high bilirubin levels that can persist for months, and relapsing hepatitis in which exacerbations can occur months after apparent recovery. Chronic infection has not been reported to occur following HAV infection.

Hepatitis A Virus Transmission

• Close personal contact
  (e.g., household contact, sex contact, child day care centers)
• Contaminated food, water
  (e.g., infected food handlers, raw shellfish)
• Blood exposure (rare)
  (e.g., injecting drug use, transfusion)

Hepatitis A (HAV) is a highly contagious virus that attacks the liver. It is the seventh most commonly reported infectious disease in the United States (behind gonorrhea, chicken pox, syphilis, AIDS, salmonellosis, and shigellosis). HAV accounts for as many as 65 percent of all viral hepatitis cases in the U.S. each year.

In 1996, approximately 29,000 cases of HAV were reported in the U.S. However,the Federal Centers for Disease Control and Prevention (CDC) estimate that there are approximately 143,000 HAV infections in the United States each year. Worldwide, there are an estimated 1.4 million cases reported annually.

There are several types of hepatitis. Hepatitis A is the most prevalent. Hepatitis A and hepatitis E are mainly transmitted through the fecal-oral route, while hepatitis B, C, and D are spread through blood or other body fluids.

There is currently no treatment for hepatitis A, although rest and proper nutrition can relieve some symptoms. The most important factor affecting the severity of the disease is age. Children less than a year old rarely show clinical signs of the illness. This means that parents and child-care workers handling soiled diapers can catch or transmit the disease without knowing they have been exposed.

Clinical manifestations of hepatitis A often pass unrecognized in children younger than two years of age. Overt hepatitis develops in the majority of infected older children and adults. In adults, approximately 22 percent will be hospitalized.

An estimated 100 deaths occur in the U.S. each year from hepatitis A. In out breaks, three people died in northern California in December, 1995, and another person died in Canada in January, 1996.

The incubation period for hepatitis A ranges from 20 to 50 days , which means that infectious patients, such as food handlers or children, can spread the disease well before they are even aware they have it. Incubation is shorter with increasing age.

Most patients begin recovery within three weeks, although some have prolonged or relapsing symptoms for up to six months.

How Is Hepatitis A Spread?
The hepatitis A virus is transmitted by the fecal-oral route, through close person-to-person contact, or by ingesting contaminated food or water. Infection has been shown to be spread by:

-- close personal contact with someone infected with hepatitis A.
-- eating foods contaminated by infected food handlers.
-- contact with infected children (who do not usually show symptoms), who can   
    then infect non-immune children or adults at home or in child-care centers.
-- ingesting raw or undercooked shellfish (e.g. oysters, clams, mussels) from  
    waters contaminated with the hepatitis A virus.
-- ingesting contaminated food or water during travel to underdeveloped areas.
-- transmission through blood transfusions or sharing needles with infected 
    people using injectable drugs.

In the United States and other developed countries, people potentially susceptible to catching hepatitis A include:

-- those who travel to less developed areas of the world where hepatitis A is  
   common. These areas include Africa, Asia (except Japan), the 
   Mediterranean  basin, Eastern Europe, the Middle East, Central and South  
   American, Mexico andparts of the Caribbean.
-- military personnel
-- individuals living in areas where hepatitis A is endemic
-- certain ethnic and geographic populations that experience cyclic epidemics
-- male homosexuals and others who engage in high-risk sexual activity
-- hemophiliacs and other recipients of therapeutic blood products
-- youngsters in child-care facilities, their families, and facility staff
-- food handlers
-- healthcare workers who treat patients infected with the virus
-- institutionalized persons and their caregivers
-- laboratory workers who handle live hepatitis A virus
-- handlers of primates that may harbor hepatitis A.

Also at risk are people who live in frequently affected communities with poor sanitation or overcrowded living conditions.

Why Worry About Children?
The highest incidence of hepatitis A is in children. Nearly 30 percent of the reported cases occur in children younger than 15. Many very young children do not show symptoms, so the unreported number is likely much higher.

Many health experts suggest that children are a silent source in spreading the disease. Approximately 45% of persons with HAV cannot identify a recognized risk factor associated with their disease, but about half of them have children under five years of age living in their households.

How Can Hepatitis A Be Prevented?
Historically, the most common preventative has been immune globulin administration, which is effective for about three to six months. Now, however,there are two vaccines that provide longer-term protection and eliminate the need for repeated shots. These vaccines typically are administered as oneinitial shot followed by a booster shot in about six to 18 months.

Prior infection with hepatitis A confers lifetime protection against a second attack. If in doubt, a blood test can determine if an individual has had hepatitis A in the past or needs protection.

What Is The Economic Impact Of Hepatitis A?
The annual direct and indirect costs of treating cases and controlling outbreaks of hepatitis A in the United States are estimated to be $200 million. Additional economic costs are incurred when adults who contract the disease miss an average of 27 days of work, which translates into approximately $2600 in lostwages for each adult case ($2600 x 150,000 cases annually = $390 million in losttime). These estimates do not include business losses in the restaurant ortourist industries related to outbreaks of the disease.

How do people get hepatitis A?

Hepatitis A is found in the stool of persons with hepatitis A. The virus is usually spread through person-to-person contact or through contaminated food and water. For example, you can get hepatitis A from an infected child if you don't wash your hands after changing a diaper or from an infected person if they don't wash their hands after going to the bathroom. If the fecal contaminant somehow gets on food - for example, if a contaminated cook handles food in a restaurant - the disease can spread quickly. A person can also get hepatitis A by drinking water that is contaminated with the virus or by eating food washed in contaminated water, such as raw or undercooked shellfish, salads, or unpeeled fruits.⁵

What are the symptoms of hepatitis A?

In those who develop symptomatic hepatitis A, flu-like symptoms, such as fever, chills, and a general feeling of weakness, may occur. Other symptoms may include anorexia, nausea, jaundice (yellowing of the eyes and skin), dark urine, light-colored stools, abdominal pain, and fatigue.

Although hepatitis A does not result in chronic infection, complete recovery from hepatitis A can be slow.⁶ In children, especially in those younger than 6 years of age, there are often no symptoms.⁴ Adult patients with hepatitis A may be quite ill for at least a month, and full recovery can take up to 6 months.¹ Up to 20% may have a relapse of the disease and may be impaired for as long as 15 months. In addition, it is estimated that 15% of patients require hospitalization for hepatitis A.⁶

Who is at increased risk of hepatitis A?

Children, teens, and adults who may be at high risk of hepatitis A or who could transmit the disease to others if they become infected include:

• Persons traveling to areas of higher endemicity for hepatitis A. These areas include but are not limited to, Africa, Asia (except Japan), the Mediterranean basin, Eastern Europe, the Middle East, Central and South America, Mexico, and parts of the Caribbean
• Persons living in or relocating to any community in the U.S. or abroad with one or more recorded hepatitis A outbreaks within the past 5 years
• Military personnel
• Persons who engage in high-risk sexual activity
• Users of illicit injectable drugs
• Hemophiliacs and other recipients of therapeutic blood products
• Employees of day-care centers
• Institutional care workers
• Laboratory workers who handle live hepatitis A virus
• Handlers of primate animals that may be harboring hepatitis A virus

Why is hepatitis A called a travel disease?

Hepatitis A is sometimes called a travel disease because it is the most frequently occurring, vaccine-preventable infection in travelers. Each year, approximately 24 million people from the United States visit, either on business or as tourists, areas where hepatitis A is endemic.⁷

The incidence of hepatitis A disease in travelers increases with the length of travel and is highest for those who stay in or visit rural areas, trek in back country, or frequently eat or drink in areas with poor sanitary conditions. However, many travelers falsely assume that the risk of hepatitis A is present only under these conditions. In fact, hepatitis A can also occur among travelers who stay only in urban areas and luxury hotels.⁷

Can I avoid hepatitis A if I don't travel?

It is possible to become infected with hepatitis A virus without ever leaving the United States. Approximately 45% of the 34,243 cases reported in the United States from 1990-1992 occurred in people with no identifiable risk factors.⁸ For example, county-wide outbreaks have been occurring in Northern California since 1993. In Shasta County alone, more than 500 cases have occurred.⁹ Outbreaks of hepatitis A in the United States have also been associated with contaminated food, with infected foodhandlers, and with day-care centers. For example, in an outbreak in Memphis, Tennessee, more than 1,000 cases have been identified and authorities believe the virus is being spread by young children.¹⁰

What steps can I take to help protect against hepatitis A?

Environmental Risks

There are things you can do to help protect yourself and others from the risk of hepatitis A.

Whether you are traveling to or living in areas where hepatitis A is endemic, or are at increased risk of contracting hepatitis A because of your work or lifestyle, most cases of hepatitis A can be avoided if you:¹¹

1. Avoid untreated tap water in drinks or ice cubes. When drinking or brushing your teeth, use only bottled or boiled water.
2. Do not eat unpeeled fruits, salads, uncooked vegetables, or raw shellfish (e.g., clams, oysters, and mussels). These foods can be contaminated with hepatitis A, even in "western" style restaurants and resorts.
3. Do not eat food or drink beverages (except commercially bottled beverages) bought from street vendors.

Personal Actions

Since no specific medicine is available to treat hepatitis A once you are infected, it is very important to prevent the infection. One of the best ways to prevent the spread of hepatitis A is easy - proper hand washing.

Proper handwashing:

1.	Use warm water	3.	Rub your soapy hands together for about 20 seconds	5.	Turn off water with paper towel
2.	Wet your hands before appyling	4.	Rinse your hands thoroughly to remove all soap	6.	Dry your hands with an air-dryer or a clean paper towel

Prevent the spread with your own bare hands

Always wash your hands thoroughly after using the bathroom and make sure everyone in your family does too - especially children. Wash your hands just before eating or preparing food and immediately after touching anything that might contaminate your hands. If possible, in a day-care setting, wear disposable gloves when changing or handling the diaper of a child who may be infected.

Vaccination

Hepatitis A may also be avoided through vaccination with immune globulin (IG) - or hepatitis A vaccine.⁴

IG contains antibodies (or protective proteins) to the hepatitis A virus. IG is relatively inexpensive and provides short-term protection against hepatitis A disease (generally 3 to 5 months).⁴

Hepatitis A vaccines also help provide longer-term protection against hepatitis A.⁴ The total duration of protection is unknown at present, but in one study, protection was demonstrated for at least 4 years. Studies are ongoing. The vaccines contain a killed or inactivated virus that does not cause hepatitis A, but does stimulate the body's immune system to make the antibodies that help protect against the virus.

Is vaccination safe?

Vaccines against hepatitis A are generally well tolerated. There may be pain, redness, tenderness, warmth, and irritation at the site where you receive the injection. Fever, abdominal pain, headache, fatigue, and allergic reactions may also occur.

Serious reactions are rare, but may occur. You should discuss potential side effects with your doctor.

As with all vaccines, vaccination with either IG or hepatitis A vaccine may not protect 100% of all those who are vaccinated.

ไวรัสตับอักเสบ เอ เบื้องต้น
ในอดีตอุบัติการของตับอักเสบจากการติดเชื้อไวรัสตับอักเสบ เอ ในเด็กอายุระหว่าง 5- 14 ปี ค่อนข้างสูง
ในประเทศที่กำลังพัฒนาเช่นประเทศไทย เด็กส่วนใหญ่ที่ได้รับเชื้อจะมีอาการไม่รุนแรงหรือไม่แสดง
หรือไม่แสดงอาการ แต่ก็สร้างภูมิคุ้มกัน
โรคทำให้ผู้ใหญ่ส่วนมากมีภูมิต้านทานต่อเชื้อนี้ ในปัจจุบัน อุบัติการของการติดเชื้อไวรัสตับอักเสบ เอ 
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ภูมิต้านทาน ผู้ใหญที่ ได้รับเชื้อจะมีอาการตับอักเสบรุนแรงกว่าเด็ก ทำให้ต้องหยุดงาน และขาดรายได้
อาการของโรคตับอักเสบ เอ จะเริ่มมีอาการ 15-50วัน หลังจากได้รับเชื้อ
อาการ ของโรคตับอักเสบจะคล้ายคลึงกันไม่ว่าจะเกิดจากไวรัสชนิดเอ หรือ บี โดยในระยะ3-7 วันแรก
จะมีไข้ต่ำๆ อ่อนเพลีย เบื่ออาหาร คลื่นไส้อาเจียน เจ็บท ี่ใต้ชายโครงขวา ต่อจากนั้นอาจมีอุจจาระสีเหลือง
ซีดลง ไข้เริ่มลดลง ผู้ป่วยหยุดอาเจียนและเริ่มอยากกินอาหารในขณะเดียวกับที่สังเกตว่ามีตัวเหลือง
ตาเหลือง(ดีซ่าน)เกิดขึ้นอาการดีซ่านนี้จะเป็นราว 1-4 สัปดาห์ ผู้ป่วยส่วนใหญ่จะหายเป็นปกติในเวลาไม่เกิน
4-8 สัปดาห์ มีบางรายที่อาจมีดีซ่านร่วมกับอุจจาระสีเหลืองซีดนานเกิน 2 เดือน แต่ที่สุดก็จะหายเป็นปกติ
ไม่มีผู้ใดกลายเป็นโรคตับอักเสบหรือตับแข็ง ยังไม่มีการรักษาเฉพาะและไม่มียาฆ่าเชื้อไวรัสตับอักเสบ เอ
การรักษาส่วนใหญ่จะเป็นการรักษาประคับประคอง โดยให้นอนพักมากๆห้ามเล่นซน ในช่วงที่มีอาการ
ตาเหลือง ควรให้หยุดเรียนอย่างน้อย 2 สัปดาห์นับตั้งแต่เริ่มมีอาการ ให้ไปโรงเรียนได้เมื่อ หายมีอาการ
อ่อนเพลีย ตาเหลือง ลดลงและปัสสาวะใสขึ้น แต่ ยังห้ามเล่นพละ จนกว่าแพทย์อนุญาต 
ในเรื่องอาหารถ้ายังมีอาการคลื่นไส้เบื่ออาหาร ให้อาหาร จำพวกแป้ง และน้ำตาลเช่น น้ำหวาน เมื่อเริ่มกิน
ได้ให้กินอาหารตามปกติ ถ้ากินอาหารไขมัน แล้วท้องอืด หรือปวดท้องให้งดไว้ก่อน ถ้ากินอาหารไม่ได้เลย
ให้พบแพทย์ นอกจากนี้ให้เฝ้าระวังภาวะแทรกซ้อนที่อาจจะเกิดขึ้นได้แม้ว่าจะพบไม่บ่อยนักคือ ภาวะตับวาย
ซึ่งเกิดจากการที่เซลตับถูกทำลายหมดโดยถ้ามีอาการผิดปกติเช่น เอะอะโวยวาย หรือซึมลง มีไข้กลับขึ้นมา
อีก ตาเหลืองขึ้นเรื่อยๆ หรือมีเลือดออกผิดปกต ิให้รีบกลับไปพบแพทย์ทันทีเนื่องจากเชื้อไวรัสตับอักเสบ เอ 
ติดต่อกันทางเดินอาหารและน้ำผู้ป่วยที่เป็นโรคตับอักเสบจากเชื้อไวรัสตับอักเสบ เอ จะขับถ่ายเชื้อนี้ ออกมา
กับอุจจาระเป็นเวลา 2 สัปดาห์ ก่อนที่จะมีอาการดีซ่าน ให้เห็น ชัดเจนดังนั้นถ้าไม่รักษาอนามัยส่วนบุคคล
ให้ดี หรือขับถ่ายไม่เป็นที่ก็จะเกิดอาการแพร่ระบาดได้ง่าย 
วิธีป้องกันคือ การให้วัคซีนซึ่งควรฉีดในวัยรุ่นหรือผู้ใหญ่ที่ยังไม่มีภูมิคุ้มกันต่อเชื้อไวรัสตับอักเสบ เอ 
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