Abstract
Hepatitis A Infection is caused by or hepatitis A virus (HAV). It is one of the most frequently occurring food-borne or water-borne diseases. Even though it is usually non-fatal it might lead to acute liver failure leading to high mortality. Infection by this virus during the early child hood is usually asymptomatic and leads to the development of life long immunity to this virus. The rate of this infection depends largely on the socioeconomic conditions of a place. The rate is very low in developed countries with good sanitary and hygienic conditions and more in developing countries with very poor sanitary conditions. However, people living in developing countries with transitional economies are considered to be at a higher risk of developing this infection Thus, conducting large-scale immunization programs against HAV is essential in these regions. This virus gets transmitted through the oral fecal route and can be prevented by adopting personal hygiene practices.
Introduction
Hepatitis is characterized by the inflammation of the liver and is caused by various factors like, attack of viruses, overconsumption of alcohol, as a side effect of certain medicines and trauma. Out of the four major types of viruses causing hepatitis, HAV or hepatitis A virus, causes acute, usually self-limiting infection of the liver. The attack by this virus is followed by the sudden and sharp rise of symptoms which persist for a short duration (less than two months) with no long-term impacts. Even though this infection is not fatal, it can cause debilitating symptoms and acute liver failure leading to high mortality. Hepatitis A infection is one of the most frequently occurring food-borne or water-borne diseases and occurs both sporadically and epidemically across the world. For example, an epidemic of hepatitis A was reported in Shanghai in 1988 which affected about 300,000 people. Approximately 1.4 million clinical cases of hepatitis A are reported across the world every year (Hepatitis A, 2013). This infection causes jaundice-like or flu-like symptoms. People suffering from this infection often need hospitalization and cannot continue with their normal work until a month. This leads to substantial medical and economic burden. The frequency of death due to this infection is approximately 3-6 deaths per 1000 reported cases (Centers for Disease Control and Prevention, 2011). The aim of this research paper is to provide information about the epidemiology, mode of transmission, symptoms, diagnosis and management of the disease. This paper also provides information about the efficiency of vaccines in prevention of the disease.
Epidemiology of Hepatitis A Infection
The rate of hepatitis infection depends on the socioeconomic development of a particular area. This disease usually does not lead to any symptoms in children and induces lifelong immunity in them, if affected by this disease during childhood. In the areas of low endemicity, for example, developed countries with good sanitary and hygienic conditions, the occurrence of this infection is noticed only in high risk group persons or as outbreaks involving a small number of people. This infection shows intermediate levels of endemicity in developing countries with transitional economies, where the sanitary conditions vary. Even though people living in these areas escape the infection during their early child hood due to the improvised sanitary conditions, they succumb to this disease during their older ages because they haven’t acquired adequate immunity. This leads to large outbreaks of HAV infections in these areas. High endemicity of HAV infection is noticed in developing countries with very poor sanitary conditions. Most of the children in these areas are affected with HAV infection with no upsurge of symptoms and acquire life long immunity, hence making clinical cases of hepatitis A uncommon (Hepatitis A vaccine, 2003).
HAV virus is a non-enveloped virus which belongs to the Picornaviridae family. Currently, four vaccines are internationally available, which are safe and effective in providing long lasting protection from this microbial disease (Centers for Disease Control and Prevention, 2011).
Mode of Transmission
HAV infection gets transmitted through the oral fecal route when a healthy person consumes food or drinks contaminated by the feces or stool of HAV infected person. This usually happens when an infected person does not adopt healthy hygienic habits such as washing hands after using the toilet, washing hands and food ingredients before preparation of food etc. Travelers are usually infected when they consume infected water or chilled beverages. Having sex with an infected partner or illegal drug use can also spread the disease. Casual contacts, as observed in schools or office, do not spread the disease (Hepatitis A: Questions and Answers, Information about the disease and vaccines, 2012).
Symptoms of Hepatitis A Infection
The prodromal phase or the onset of the disease is marked by flu-like symptoms including: gastrointestinal problems like nausea, vomiting, anorexia and abdominal discomfort, occasional headache, constipation, diarrhea, itchiness, cough and pharyngitis. There are no specific symptoms for the identification of this disease during the initial stages. It generally takes 15-50 days for the symptoms to appear after a person comes in close contact with an infected person. This phase is followed by jaundice, which is marked by yellowing of the skin and eyes, dark urine and pale stools. Symptoms like fatigue, nausea, and vomiting increase with the progression of jaundice. Abnormal enlargement of the liver, spleen and lymph nodes is often observed during examination. These symptoms usually last for two months but, in rare cases can also continue till 6 months. Symptoms observed during the convalescent stage include physical discomfort, hepatic tenderness, and irregularities in liver functioning (Hepatitis A -Summary, 2010) (Hepatitis A: Questions and Answers, Information about the disease and vaccines, 2012).
Diagnosis of Hepatitis A Infection
The diagnosis of this disease is based upon symptoms observed and laboratory tests. A blood test is carried to test the presence of IgM antibodies to hepatitis A virus (anti- HAV antibodies). This test is known as “IgM class antibody to hepatitis A virus”. Blood tests also help to detect if the person was infected with this virus in the past. This test is known as “total hepatitis A antibody test”. Hence, infection by this virus in the past or a mere suspicion due to exposure to the virus can also be ruled out by this test. Elevated levels of Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) in serum, due to jaundice can also be detected through liver function tests. The levels are usually higher than 1000 IU/L. An elevated level of Bilirubin (up to 500 micromoles/L) also indicates the presence of infection (Hepatitis A: Questions and Answers, Information about the disease and vaccines, 2012) (Hepatitis A –Investigations, 2010).
Treatment of Hepatitis A Infection
HAV infection cannot be directly cured as there are no medicines available which can treat this disease. An infected person is managed with only supportive care, which includes bed rest, pain relief medications like ibuprofen and treatment of nausea and itch. Therapy also focuses on rehydration and nutritional support as water and nutrients lost through vomiting and diarrhea should be replaced. The liver function and prothrombin time (time taken by plasma to clot) needs to be monitored from time to time. The patient needs to be hospitalized when symptoms become very severe (Hepatitis A: Questions and Answers, Information about the disease and vaccines, 2012) (Hepatitis A -Summary, 2010).
Why is prevention of hepatitis A infection through vaccines essential?
Even though hepatitis A is usually self-limiting and case-fatality rate is generally low, the suffering of the patient as a result of the infection is a point of concern. Moreover, an individual is put to a huge economic burden as, direct and indirect medical costs including the infection control measures are high. This infection imposes huge economic burden on the society, especially in countries showing low or intermediate endemicity. The chances of infection being spread to healthy individuals from an infected person are more during the first two weeks before the infected person develops symptoms like yellowing of skin and eyes. This makes it difficult to arrest the transmission of the infection from the infected person, as the person does not even realize that he/she has been infected. None of the currently available drugs have the potency to cure HAV infection and an effective antiviral medication which can arrest this virus has not yet come up as a realistic option. Socioeconomic development can control the transmission of this disease to some extent, as it is associated with improved sanitation and health education. But socioeconomic development is relatively low in some parts of the world (Hepatitis A vaccine, 2003) (Hepatitis A: Questions and Answers, Information about the disease and vaccines, 2012).
The above discussed factors make the prevention of hepatitis A infection through immunization very essential. The protective role of anti-HAV antibodies developed in response to infection which persist for life has been well studied. These antibodies protect an individual from the re-occurrence of the disease for the rest of the life. Hence, immunization through vaccines along with improved sanitation and food safety are highly efficient in combating HAV infection. Both pre- and post-exposure prophylaxis of the disease is possible with the help of immunoglobulins. For example, a person can be immunized shortly before entering a disease-endemic area or after being exposed to hepatitis A virus (Hepatitis A vaccine, 2003).
WHO’s Recommendations on Hepatitis A Vaccine
According to WHO, all the currently available vaccines against hepatitis A are absolutely safe as they contain an inactivated virus and none of the parts of the vaccine is live. However, these vaccines cannot be administered to children below one year of age. This vaccine can be safely injected to children between their first and second birthdays. Children and adolescents living in highly endemic areas should be essentially vaccinated. Apart from this, people who are frequent travelers, men who have sex with men, people who use injectable or non-injectable illicit drugs, people suffering from chronic liver diseases, people suffering from blood clotting disorders, persons treated with clotting factor concentrates and persons handling hepatitis A virus in research laboratories should get immunized with hepatitis A vaccine. Under special situations like outbreaks of hepatitis A infection or exposure to the virus, unvaccinated children and adolescents are recommended to get hepatitis A vaccine. WHO recommends two doses of hepatitis A vaccine with a 6 months gap between the two doses of vaccine. People who show severe life-threatening allergic reaction to hepatitis A vaccine should avoid the second dose of vaccine. Pregnant women should take the opinion of the doctor before getting vaccinated. The risks associated with this vaccine are very mild like soreness, loss of appetite, headaches and tiredness (Centers for Disease Control and Prevention, 2011). These problems persist for 1 or 2 days, hence making this vaccine much safer.
Criteria behind Large-Scale Immunization Programmes against HAV
Large-scale immunization programs against HAV should be carefully planned based upon factors like endemicity of the diseases in the targeted area and number of people susceptible to this infection. In highly endemic areas, almost everyone gets infected during the early childhood without showing any symptoms. As a result, they acquire natural immunity against this infection hence preventing clinical hepatitis A during adolescence and adulthood. In these areas, large-scale immunization programs or inclusion of the vaccine in routine childhood immunizations is not recommended. The risk of hepatitis A infection in adults is relatively high in the areas of intermediate disease endemicity, making it a significant public health burden. Large-scale childhood vaccination is considered to be the apt method of prevention along with health education and improved sanitation in these areas. Hence, countries like U.S., Israel, China, etc have introduced this vaccine in routine childhood immunizations.
Conclusion
Hepatitis A is a preventable disease and in case of out breaks, the transmission of the virus can be arrested by taking care of few factors like, supply of safe drinking water, providing education about personal hygiene practices and proper disposal of sewage within communities.
References
Centers for Disease Control And Prevention. (2011) Hepatitis A Vaccine, What You Need to Know. Vaccine Information Statement. U.S. Department of health and human services.
Hepatitis A. (2013). Who.int. Retrieved Aug 26, 2013, from
http://www.who.int/mediacentre/factsheets/fs328/en/
Hepatitis A vaccine. (2003). Who.int. Retrieved Aug 26, 2013, from
http://www.who.int/vaccines/en/hepatitisa.shtml
Hepatitis A: Questions and Answers, Information about the disease and vaccines. (2012). Retrieved Aug 26, 2013, from. www.immunize.org
Hepatitis A - Summary. (2010). Nice.org.uk. Retrieved Aug 26, 2013, from
http://cks.nice.org.uk/hepatitis-a#!topicsummary
Hepatitis A - Investigations. (2010). Nice.org.uk. Retrieved Aug 26, 2013, from
http://cks.nice.org.uk/hepatitis-a#!diagnosissub:2
No comments:
Post a Comment