Hepatitis B is an infectious disease caused by hepatitis B virus (HBV) that damages liver resulting in its inflammation.
Hepatitis B virus influences the functions of the liver replicating in its cells that are called hepatocytes. Hepatitis B can be acute (self-limited) or chronic (long-term). Patients with self-limited infection recover in three weeks or months.
Over 95% of patients who were infected by the virus in the adulthood make a full recovery and develop a protective immunity against the virus. However, this probability drops to 30% in smaller children, and only 5% of newborns that were infected by their mother in the process of childbirth get rid of the virus. With a 40% probability, these people will die of cirrhosis or hepatocellular carcinoma. 70% of those infected in the age from 1 to 7 will discard the infection.
According to the estimates, 350 million people of the world were infected in 2004. National and regional spread varies from 10% in Asia to less than 0.5% in the USA and Northern Europe. Ways of contagion include vertical transmission (at birth), horizontal transmission in the early years of life (bites, injuries, and sanitary habits), and horizontal transmission in adulthood (sexual contacts, intravenous injection of preparations).
Hepatitis C is an infectious disease caused by hepatitis C virus (HCV) that damages mainly the liver. Infection is often asymptomatic, however, chronic infection leads to fibrosis and, eventually, cirrhosis or liver cancer (hepatocarcinoma). Transmission takes place parenterally due to virus penetration into blood during intravenous injection of drugs or blood transfusion because of using poorly sterilized medical accessories. The virus is preserved in the liver of about 85% of infected people. Usually, hepatitis C is treated by long-term combined anti-virus therapy, and 50-80% of people undergoing such treatment recover.
According to some estimates, 130-170 million people in the world are infected by hepatitis C.
Hepatitis C is often asymptomatic, but chronic infection may cause fibrosis, and in several years - cirrhosis. If cirrhosis progresses, liver failure occurs, and cancer/cirrhosis of liver may develop. Dilatation of esophagus and stomach veins may cause fatal bleeding.
Pegylated interferon and ribavirin are the standard HCV medications. Patients with cirrhosis or liver cancer require liver transplantation, however, the virus usually recurs after transplantation.
What are sexually transmitted infections and how are they transmitted?
STIs, which are caused by 30 different bacteria, viruses and parasites, are usually transmitted during sexual contacts, including vaginal, anal, and oral sex.
Some STIs may be transmitted through skin sexual contact. Microorganisms causing STIs may also be transmitted in the course of blood product transfusion and tissue transplantation. Many STIs, including chlamydiosis, gonorrhea, hepatitis B, HIV, HPV, HSV-2, and syphilis may be transmitted from the mother to the child during pregnancy and childbearing.
A person may have STIs without any manifest symptoms. Therefore, the term "sexually transmitted infection" is broader than the term "sexually transmitted disease" (STD). General symptoms of STDs include vaginal discharge, urethral discharge in men, genital ulcers, and abdominal pain.
The highest incidence is connected with eight out of over 30 known pathogens that are transmitted in the course of sexual contacts. Today, 4 out of 8 of these infections can be treated. These are syphilis, gonorrhea, chlamydiosis, and trichomoniasis. The other four, such as hepatitis B, herpes, HIV, and HPV are viral diseases that cannot be cured, but treatment may decrease their influence.
Treatment of STIs
At present, some STIs can be effectively treated.
Three bacterial STIs (chlamydiosis, gonorrhea, and syphilis), and one parasitic STI (trichomoniasis) can, as a rule, be treated using effective one-dose antibiotics.
What concerns herpes and HIV, most effective medications here include antiretroviral agents that can mitigate the course of the disease, but they cannot cure it.
What concerns hepatitis B, there is immunomodulator (interferon) and antiretroviral agents that help fight the virus and slow down the destruction of the liver.
The resistance of STIs to antibiotics has grown dramatically over the last years limiting treatment options. The appearance of gonorrhea with reduced sensitivity to the “last line” therapy (oral and injectional cephalosporins) accompanied by resistance to antimicrobial agents is already manifested in regard to penicillins, sulphonamides, tetracyclines, quinolones, and macrolides, and caused the fact that gonococcus became a microorganism with multiple drug resistance. The resistance of STIs to antimicrobial agents is not that spread, but it does exist, which makes prevention and immediate treatment critical.
Vaccines and other biomedical measures
There are safe and effective vaccines against two STIs – hepatitis B and human papilloma virus (HPV). These vaccines are a great achievement in the area of STI prevention. Hepatitis B vaccine is included into the program of child immunization in 93% of countries. According to the estimates, it has already prevented 1.3 lethal cases caused by chronic liver disease and cancer.
HPV vaccine is available as a part of regular immunization programs in 45 countries, the majority of which are countries with the high and medium level of income. In the next decade, the HPV vaccine may prevent more than 4 million deaths of women in countries with low and medium income level, which have the highest incidence of cervical cancer, on condition that 70% of the population will be vaccinated.
A certain success has been reached in research aimed at the creation of herpes and HIV vaccines, however, there are no acceptable vaccines against these diseases yet. Vaccines against chlamydiosis, gonorrhea, syphilis, and trichomoniasis are being developed.