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The pathway and mode of infection of virus hepatitis
Virus hepatitis is a common pediatric infection disease, the incidence, acute or severe cases and mortality of which are higher than those of adults. We may first look at the different pathways and mode of infection of different types of hepatitis virus so as to understand the dissemination and seriousness of pediatric hepatitis and to pay greater attention to gain more knowledge on our children’s health, to the early detection and treatment of the disease and to avoid their prolonged suffering from the attack of hepatophilic virus. In this way, the quality of health of the next generation can be improved and the effort used would be much less.
The “coaecrvation phenomenon” in virus hepatitis transmission
In virus hepatitis, the type most concerned is hepatitis B, because if the mother is a virus carrier, she may transmit the virus to the newborn. If the maternal blood is examined to be HBeAg positive (hepatitis B nuclear antigen positive), the chance of infection in the infant is 90% or more; but if HBe antibody positive (hepatitis B antibody positive), the chance of infection in the infant is comparatively small, usually 10% -15%.
Besides mother-child transmission, hepatitis B can also be transmitted through close contact between family members, and teeth brushing, use of bathing brush and razor blades in daily life can also transmit hepatitis B virus infection. Transmission through saliva and blood should be considered also as an important pathway of infection, because 30%-50% of chronic hepatitis B patients’ saliva show HBsAg (hepatitis B surface antigen) and attention should also be paid to spread by female menstrual blood. Therefore, to decrease the chance of dissemination, it is important to request good daily life habits, not to feed infants with chewed food, proper disposal of menstrual blood pollutant, washing hands before feeding and tableware sanitizing. It is only through these measures that family hepatitis virus infection, the “coacervation phenomenon” (a number of individuals in one family attacked by virus infection) can be prevented.
Clinical symptoms of pediatric hepatitis easily neglected
There is great difference in symptoms between mild and severe cases of virus hepatitis. In severe cases, the onset is acute, for example, in acute icterohepatitis, after the latent period, there is fever, fatigue, sleepiness, generalized tiredness, anorexia, nausea, vomiting, diarrhea, constipation or common cold symptoms. About 2-8 days later, there is appearance of marked yellowish urine, the color similar to black tea or even sauce and it is then followed by jaundice of the sclera and skin, hepatomegaly, percussion tenderness of hepatic region or even telangiectasis of face, vascular spider and liver palm. The disease is not easy to be misdiagnosed because of the presence of jaundice, so the patient is usually discovered in time, isolated and treated accordingly.
But the anicteric type of hepatitis does not have jaundice, therefore, its symptoms may be mistaken as other virus diseases, such as common cold, influenza, upper respiratory tract infection, tonsillitis, trachitis and acute gastroentiritis. In fact, anicteric hepatitis has a higher incidence than the icteric type. As to the proportion of the clinical type to the non-clinical type, it is estimated to be 1 : 40, that is in 40 individuals with virus hepatitis, only one presents obvious symptoms. This condition reveals the popularity of hepatitis virus infection and that it is very easy to be neglected and misdiagnosed. Therefore, it should be noticed that the non-clinical typeincludes sub-clinically infected patients carrying hepatitis surface antigens but without symptoms. Attention should also be paid to latently infected patients carrying hepatitis antigens but without symptoms and chronic active hepatitis, chronic persisting hepatitis patients. If these pediatric patients are not discovered, they would not receive adequate treatment, their health and development would be impaired and the body constitution of the next generation is directly affected. Therefore, the first thing is to increase alertness on infections by hepatitis virus. If a direct relative or any person in close contact with the child has a history of acute or chronic hepatitis, cirrhosis or carcinoma of liver, or whose blood examination proves to be “antigen carrier” of hepatitis virus, or has abnormality of liver function, it should lead one to consider that the child has already been infected.
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| Types of virus hepatitis
Recognize the danger of hepatophilic virus………
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Hepatitis A
Hepatitis A spreads all over the world; the places with high incidence include southeastern Asia, Africa, South America and China. 80% of newborn infants receive hepatitis A antibodies from the maternal placental circulation. But these antibodies mostly disappear in two years and infants have very high susceptibility to hepatitis A. During their growth, most of the children acquire immunity through subclinical infection (sub-clinical infection means that one has hepatitis A infection with no clinical symptoms, no liver function damage but if that person is an antigen carrier, one can excrete virus and transmit hepatitis A). This kind of immunity is formed by production of antibodies after hepatitis A infection. It indicates previous hepatitis A virus attack, but if these are clinical symptoms and hepatomegaly, treatment should be instituted.
According to survey of China cities, children aging 2-10 years make up the chief human group suffering from hepatitis A; they consist mainly of children before and within school age. Statistics show that children aged 1-9 years have 52.6% positive hepatitis A antibodies, those aged 10-19 years have 98% and those over 29 years have 100% of positive hepatitis A antibodies. From this we can see the popularity of hepatitis a infection. It is commonly acknowledged that hepatitis A does not turn into chronic hepatitis. But there is report demonstrating that hepatitis A can similarly induce chronic hepatitis. (Weigl and Bach had reported that in 1283 cases of acute hepatitis A, 6.9% developed into chronic persisting hepatitis and 0.4% into chronic active hepatitis. In addition, Meier et al studied the serology, clinical biochemistry and a part of the liver biopsies of 25 hepatitis A patients and found that 20% manifested a persisting or chronic course with persistent increase of transaminase).
Oral transmission of disease
Hepatitis A virus is usually transmitted through the fecal-oral pathway. Stools from hepatitis A patients and subclinically infected sufferers are excreted with viruses; they contaminate food, water, tableware, utensils, toys and spread the disease. When the susceptible community increases to a certain proportion, a cyclic explosion of epidemic would occur. After an episode of epidemic spread, 80% of the susceptible community may be infected and then the epidemic stops. When the susceptible community increases to a certain proportion, the invasion of virus would evoke another episode of epidemic.
The present acknowledgement is that there is no persistent “antigen carrier” in hepatitis A virus and the origins of infection are the acute phase and subclinically infected patients. A life time immunity can only be achieved when human beings are continuously in a repeatedly infected situation. It is considered that hepatitis A virus can be alive for 12 months in fresh-water as well as salt water and for several days inside food. It will be dead if boiled in water for 5 minutes under 100°C. Therefore, the basic way to prevent hepatitis A is to put stress on individual hygiene, teach children to keep sanitary habits and prevent transmission of disease by mouth.
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Hepatitis B
Hepatitis B is a worldwide infectious disease. Its danger is more serious than other types of hepatitis. It is estimated that in the world 350 million people are “antigen carriers”, in which three fourths are Asians. The proportion of male to female is 6:1 in which at least 20% have various degrees of chronic active hepatitis and cirrhosis of liver and part of these cases may eventually turn into carcinoma of liver.
In China, about 40%-60% of the population has been infected by hepatitis B virus. In Hong Kong, about 40% of the population has been infected by this virus. The 1st peak period of infection by hepatitis B virus is before 10 years of age; the 2nd peak period is 30-40 years. Hepatitis B virus can pass through various body fluids (blood, semen, leukorrheal discharge, saliva, milk, menstrual blood, tears, urine and sweat) and be excreted, causing dissemination of infection, especially through blood and semen. Therefore, everyone carrying hepatitis B virus can transmit hepatitis B; those suffering from acute or chronic hepatitis B and the “antigen carriers” and other patients with positive antigen results (patients with cirrhosis or carcinoma of liver and other patients not having liver disease) are all origins of infection. In particular, the asymptomatic “antigen carriers” exist widely in the community, they remain unnoticed and therefore potentiate a greater degree of danger.
According to the epidemiological survey of our country in 1979-1980, these were over 120 million asymptomatic hepatitis B antigen carriers, the number of male is more than female. In Hong Kong, these are also nearly 600 thousand hepatitis B patients with positive surface antigen. As to age distribution in our country, the incidence is the highest before 10 years of age, and it decreases along with the increase of age. The highest incidence of hepatitis B is in the children group; the chief reason is that when the mother has hepatitis B, the infection is transmitted through the mother-child pathway.
Three possible ways of transmission
These are 3 possible ways of transmission in hepatitis B:
Mother-infant infection is the chief source of hepatitis B
Mother-infant infection is the most important pathway to transmission in hepatitis B. It is usually considered that in the community 35%-50% of carriers of hepatitis B surface antigens (antigen carrier) come from mother-infant transmission. In 1984, Beasiey pointed out that in countries over the world, the viruses in the maternal bodies with “positive” chronic hepatitis B surface antigen have different incidences of infection in the perinatal period. In Europe and America, the incidence rate is 10%, in Africa 25%-30%, Asia 30%-70% and in China 60%.
In recent years, Chinese investigations revealed that in screenings pregnant women with positive hepatitis B surface antigen had an incidence of 5%-10% in which 1/3 also have positive hepatitis B nuclear antigen (the commonly called double positive). If the mothers have “positive” hepatitis B surface antigen, 40%-50% of their children would become “antigen carriers”. If the mothers have also positive hepatitis B nuclear antigen, 63%-90% of their children would become hepatitis B “antigen carriers” within half a year. Not a few studies have demonstrated that if the mothers is “double positive”, among the siblings, there would appear a conspicuous “family coacervation phenomenon” of hepatitis B surface antigen (i.e. a number of people in a family infected by the virus and become “antigen carriers”).
In our country, the mother is the chief constituent of “family coacervation” of hepatitis B surface antigen, the mother’s effect on the infection of her children is strong and steady. Therefore, the prevention of transmission of virus from mother to children is of decisive significance to the control of hepatitis.
Caution on close contact infection
Besides mother-child transmission, close contact among family members (including baby-sitter) is also a very important way of transmission. Because there is an obvious phenomenon of hepatitis B surface antigen “family coacervation” among siblings, close contact can easily promote transmission of the infection. In addition, in different situations (in family, kindergarten, child-care center, school, hospital), the abrased mucosa or skin of the infant may be in contact with contaminated blood, drugs or medical instrument and then be infected by hepatitis B.
Increasing clinical evidences show that the main feature of hepatitis B virus infection is chronicity(慢性化). The danger to human beings is the formation of persistent infection; the smaller is the age of infection, the greater is the chance of becoming persistent infection. From the statistics, it is found that infants infected in the puerperium have a 80% possibility to become carrier of hepatitis B virus surface antigen, infection in childhood is about 30% and infection in adults, the possibility of becoming a persistent infection is below 5%. Therefore, infection by hepatitis B virus during infantile stage and childhood is most dangerous. It is estimated that in the community, 35%-50% of the people carrying hepatitis B virus surface antigen are infected during the maternal-infant puerperial period.
Attaching importance to treatment of pediatric hepatitis is the best policy
The prognosis of infantile pediatric hepatitis is not so good; most of the ones infected at newborn and infantile age would become chronic antigen carriers and chronic hepatitis sufferers. So, according to the above data, in the hepatitis B highly prevalent districts, the chance of infection by hepatitis B virus is very high and the prognosis is also very poor. Many infantile patients are infected not by their own will and they have to carry the disease throughout life with the repeated appearance of clinical symptoms of chronic hepatitis. Hepatitis virus affect their health in a life time and it is regretful that up to the present, many people do not care much for infantile and childhood chronic hepatitis; they do not understand the prevalence and harmfulness of the disease. Some people consider that there is no method to cure hepatitis radically and therefore they give up the treatment; others do not believe the effectiveness of Chinese drugs and refuse TCM therapy. Actually, these are extremely unwise considerations. From now onwards, the key point in prevention and treatment of hepatitis B should be put on infants and children in whom sufferers of hepatitis B can achieve clinical cure or not is of utmost importance.
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Hepatitis C
The distribution of hepatitis C is worldwide showing that human beings are susceptible to hepatitis C virus. Among the sporadic hepatitis cases seen at the cities of many countries, hepatitis C takes up a proportion of 11.8%-23.8% in China and in 321 cases of acute sporadic virus hepatitis examinations, hepatitis C accounts for 6.2%. According to American statistics, hepatitis C accounts for 20%-40% of acute hepatitis cases and it is estimated that there are 200-300 thousand people suffering from hepatitis C every year.
Hepatitis C virus has not been successfully isolated and cultured at the present time and because the amount of virus nucleic acid and antigen in the patient’s blood is extremely minimal, it is not so easy to be detected by the commonly used methods. Recently, an investigation about hepatitis C in China revealed that the genetic constituent of hepatitis C virus is simple and only the type 2 and type 3 are in wide epidemic spread and its distribution also shown significant regional difference. In the south, the one in wide spread is type 2 and in the north, one half belongs to type 3. This investigation also certifies the ability of detecting Chinese hepatitis C positive transfusion donors by the international standard reagent and it was found that 13% of the virus “antigen carriers” could not be detected.
The chief source of infection in hepatitis C is virus carriers, including acute and chronic hepatitis C patients, subclinical patients and asymptomatic virus disseminators. They may persistently carry the virus over 12 years. It is now clear that the chief routes of hepatitis C infection are blood transfusion, blood products, injection, sexual life, mother-infant transmission and close contact. According to statistics, 50% of hepatitis C cases have no history of blood transfusion or use of blood products or history of injection; these cases are infected through close contact. Hepatitis C, in general, has comparatively mild symptoms, mostly anicteric and it is estimated that asymptomatic latent infections are even more. At least 40%-50% of hepatitis C patients would change into chronic hepatitis, the proportion is much higher than that in hepatitis B and in the end they have a higher tendency to develop into cirrhosis or carcinoma of liver. (Some data indicated asymptomatic hepatitis C patients can also develop into cirrhosis of liver and 60% of primary hepatic carcinoma patients show positive hepatitis C antibodies).
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Hepatitis D
Hepatitis D virus is a kind of defective virus which requires the supplement of type B hepatitis virus to proceed replication and infection, so that it becomes pathogenic only with the company of hepatitis B virus infection. Due to the correlation of hepatitis D virus and hepatitis B virus, the infection can be divided intocommon infection and overlapping infection. The former is usually acute hepatitis, a few may develop severe hepatitis or turns into chronic hepatitis, but most of the acute hepatitis D cases would pass a benign course. The latter has already had liver damage due to the existing hepatitis B, therefore, most of the patients (70%-90%) would have aggravation of the disease and the tendency to turn into chronic hepatitis and cirrhosis of liver increases.
The distribution of hepatitis D is worldwide. According to statistics, at least 350 million people in the world are carriers of hepatitis B surface antigen, in which 5% are infected by hepatitis D virus; therefore, at least 15 million are concurrent sufferers of hepatitis D. In our country, it is chiefly found in Inner Mongolia, Tibet and Xinjiang. The mode of infection of hepatitis D is basically similar to hepatitis B, but mother-infant transmission is comparatively less. Its transmission is chiefly through the antigen carrying mother to the newborn child and close contact between family members through infected body fluids forming a horizontal transmission and “family coacervation” phenomenon may also occur (a number of persons infected in a family). But sexual transmission in hepatitis D is more important; the use of unclean injections or promiscuous sexual relationship (homosexuality or bisexuality) are the chief routes of infection. Hepatitis D cases often times develop into chronic hepatitis or cirrhosis of liver or may turn into severs hepatitis.
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Hepatitis E
The epidemiology of hepatitis E is similar to hepatitis A, the spread being through fecal-oral transmission. Epidemic is induced by contamination of the source of water supply or by food ingestion. Its incidence, to a high degree, is related to the level of hygiene in the community, displaying in the form of local epidemics and fulminant epidemics. It has apparent seasonal characteristics and is frequently seen in the rainy seasons or after floods. In an investigation of 321 cases of sporadic acute virus hepatitis in our country, hepatitis E accounts for 10.28%. This disease has a higher incidence in the 20-40 years age group, male prevails over female. But in children, the infection usually belongs to the subclinical type and therefore may be neglected.
Hepatitis E may also be transmitted in daily life contact. In general, it is considered that this disease would not develop into chronic hepatitis, but its incidence is high and is more severe in pregnant woman, so it is easier to cause abortion and stillbirth. The mortality of this disease reaches 10%-20%, so one must treat it with prudence. Patients have a certain degree of immunity after hepatitis E infection and sufferers of second attack have not yet been discovered.
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Hepatitis F & Hepatitis G
The above mentioned five types of hepatitis were ascertained in September 1989 at the International Meeting on non Type A non Type B Hepatitis and Blood Transmitting Infectious Diseases held in Japan. But according to later reports, there were also other types of hepatitis discovered, namely, hepatitis F and hepatitis G.
• Hepatitis F (HFV) and other intestinal tract transmitting new types of virus hepatitis had been reported in Britain, Italy, France, America, India and Germany and it was considered to be a double chain DNA virus.
• There were many reports about hepatitis G (HGV) and other blood transmitting new types of virus hepatitis. In our country, it was also found to be a RNA virus under the branch of yellow virus. It is transmitted through blood and can turn into chronic hepatitis. In addition, the GBV virus was also found, the type C of which produces infection through blood transmission and therefore, it is also called GBV-C/HGV. But, it is recognized now that there may be other hepatitis virus transmitted by blood.
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| By WONG Kwok Hung
translated by Professor ZHENG Hua En in July 2005 |
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