Hepatitis B: epidemiology

The main reservoir and source of HBV are patients with acute hepatitis B. Patients with chronic HBV infection (virus carriers and patients with CHB), whose number on the globe exceeds 300 million people.

In patients with HBV infection, HBsAg and HBV DNA are detected in the blood, urine, saliva, bile, tears, feces, breast milk, vaginal secretion, sperm, cerebrospinal fluid, cord blood. However, only blood, semen and, possibly, saliva present a real epidemiological danger, since in other fluids the concentration of the virus is very small. The main transmission factor is blood. An infectious dose of the virus can be contained in 0.0005 ml of blood. Viral hepatitis B is characterized by a multiplicity of transmission routes (natural and artificial): contact, vertical and official (parenteral manipulation, organ transplantation) of the transmission route are possible. The sexual way of transmission of HBV is extremely effective. Among those infected with the hepatitis B virus, the proportion of drug users practicing intravenous drug use is high. In this regard, even in highly developed countries, the significant infection of addicts, as well as homo- and heterosexuals with a large number of sexual partners, maintains the high epidemic potential of HBV infection. Infection with viral hepatitis B is possible even when communicating with a patient or a virus carrier if the integrity of the mucous membranes and skin is compromised. In these cases, HBV is implanted through damaged skin (microtrauma), with direct contact with the source of infection, or when used together with various household items and personal hygiene (blood-soaked underwear, scissors, nail files, toothbrushes, razors, scouring pads etc. ). Of particular importance is the transmission of HBV by a vertical route from a pregnant woman (a patient with acute hepatitis B or chronic HBV infection) to a fetus or a newborn. In this case, transplacental transmission of the virus is possible (about 8% of cases among infected children) or, more often. Infection in the process of delivery when the newborn is in contact with infected amniotic fluid, vaginal secretion. The risk of infection increases significantly if acute hepatitis B develops in a woman in the third trimester of pregnancy and birth occurs during the HBeAg-emia or child is born by a woman with chronic hepatitis B with HBeAg in the blood.

At present, the risk of infection with blood transfusion has sharply decreased, as all donor blood is checked for HBsAg and anti-HBcIgG. Infection with viral hepatitis B is possible with various parenteral medical and non-medical interventions, accompanied by a violation of the integrity of the skin or mucous membranes (injections, dental, endoscopic, gynecological examinations, cosmetic procedures, piercing, tattooing, etc.) if the rules of sterilization of instruments are violated. Groups of risk of infection with viral hepatitis B are patients of hemodialysis departments, burn centers, hematological units. Tuberculosis hospitals, cardiovascular surgery centers, health workers who have contact with blood: procedural and operating sisters. Anaesthesiologists-resuscitators, obstetrician-gynecologists, surgeons, dentists, etc. The susceptibility to viral hepatitis B is high. The age-related susceptibility to viral hepatitis B has a number of characteristics, mainly related to the probability of chronic infection. The risk of developing chronic HBV infection after infection with the hepatitis B virus ranges from 90% in newborns born to HBeAg-positive mothers, to 25-30% in infants and children under 5 years of age, and is less than 10% in adults. Immunity after a previous viral hepatitis B is prolonged, perhaps, for life. Repeated cases of viral hepatitis B are observed exceptionally rarely.

The prevalence of hepatitis B (including the incidence of acute forms and the percentage of virus carriers) varies significantly in different regions of the world. The criterion for assessing prevalence is the frequency of detection of HBsAg in a healthy population (donors). Low prevalence is considered to be regions with carrier frequency of less than 2%, medium - 2-7%, more than 7% - high. In Australia, Central Europe, the United States and Canada, a low carrier level (no more than 1%) is noted, and in South-East Asia, South China, Taiwan, and tropical Africa, 20-50% of the population are carriers of HBsAg. The proportion of people aged 15-29 years is 60-85% of the total number of patients with acute hepatitis B, which is associated with the prevalence of injecting drug use and risky sexual behavior without the use of barrier methods of contraception.

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13]