At present, virus infection is the most prevalent disease in the world, about 60% of the infectious disease is caused by a virus, and new viruses have been found constantly, which is highly contagious and has high fatality rate, causing serious harm to human health. Antiviral therapy is the fundamental treatment of viral infectious diseases. For acute infection, antiviral therapy helps to reduce symptoms and shorten the course of treatment; and for chronic persistent infection is the treatment of the fundamental, such as AIDS, hepatitis B, hepatitis C and so on. Different viral infections cause different disorders and require different antiviral medications.
Although over the years the development of gene engineering and chemical synthesis of antiviral drugs for clinical use of drugs to control the virus infection and provide more choices and opportunities, and it has been confirmed to have clinical value of antiviral drugs is still one of the few, drug indications are very limited.
In particular, it is difficult to achieve a cure for some of the chronic viral infections. Because the virus is obligate intracellular parasites, its proliferation depends on biosynthesis of the host cell, some virus nucleic acid directly integrated into the host cell gene. Therefore, it is necessary to select antiviral drugs according to the characteristics of the virus. Antiviral drugs should selectively destroy or inhibit the virus inside and outside of the cell, while for normal cells, at least for non-infected cells do not produce lethal damage. Therefore, it is more difficult to make antiviral drugs that have an inhibitory effect on the intracellular virus, to achieve clinical antiviral effect, but not on the metabolism of the host cell. In addition, the better effect of antiviral drugs to protect uninfected cells and early infection cell that have not yet produced significant lesions, however, the symptoms of viral infectious diseases are lack of specificity, it is not easy to diagnose early, when the clinical symptoms appear of virus infection, the virus proliferation has reached a certain degree. For example, a large number of viruses have been infected and release in the cell proliferation When the prevalence of influenza and Japanese encephalitis, and the body is in viremia or viremia late stage, has caused tissue damage, then we should check with effective virus drugs, although it is possible to control the further proliferation and spread of the virus, but often "too late", has not played a decisive role in the treatment. Some virus-induced syndromes are common and relatively benign or self-limiting, so that only drugs with a high therapeutic index (ratio of efficacy to toxicity) can be accepted. So it is still very difficult task to develop safe and effective, selective, easy to use antiviral drugs.