It is said that some viruses are responsible for cancer causing tumours in humans and other animals, this type of viruses are called viral oncogenes. Human papilloma virus that causes cervical and other type of cancers is the best example for this. These viruses mainly act by completely altering the genetic structure of that host cells. Modern medicine has developed vaccines against these types of viruses. By use of vaccines at the right time we can prevent the frequency of these tumours.

Few diseases caused by the viruses are fatal, at times infected person will die within a short span of time. Moreover some of these are not having specific target drugs like HIVAIDS. viruses infect the major functional organs and interfere with the normal functioning of the body. Some of the deadly viral diseases that human race has ever witnessed are Ebola, smallpox, hepatitis, Rabies, Yellow fever etc. Antiviral medication is used to cure these diseases.

The study of viruses at the molecular level is called molecular virology. Since viruses are  acellular organisms they replicate and live inside the host cells by altering their genetic makeup. They can infect different organisms like plants, animals, fungi, bacteria. Due to this reason, viruses are having a vast biological and genetic diversity and understanding this diversity is the key for the treatment of any viral diseases.

The study of the viruses which infect nervous system is called Neuro virology. Viral infections of brain are a bit complicated to understand due to the various underlying reasons. One of the main reasons is that the virus acts in an unpredictable manner due to this much of the experiments carried out are based on testing the hypothesis which is a major drawback.

Viral infections of the brain are less common than any other infections because unlike other organ infections brain infections depend upon the breakdown and passage through the blood brain barrier which occurs very rarely. Viruses take advantage of such events and cause neurological problems through a number of mechanisms like causing cell lysis, inducing apoptosis or by creating secondary damage due to release of glutamate. Viruses such as rabies do not kill neurons but they alter cellular transcriptional pathways to express viral genes rather than neuronal genes, these results in neurons that no longer function as neurons, but look normal upon routine pathological examination making it difficult for the pathologist to identify the virus.

  Due to all these reasons we need to have a complete understanding and knowledge of viruses and their makeup in order to identify and treat that infection.

Immunology is the branch of biomedical sciences that covers all aspects of the immune system in all multicellular organisms such as bacteria, viruses, protozoa, and fungi, and also parasitic organisms, such as helminth worms. Cell signalling is part of a complex system of communication that administers basic cellular activities and coordinates cell activities. A Neutralizing antibody is an antibody which safeguards a cell from an antigen or infectious body by inhibiting or neutralizing any effect it has biologically. Cell-mediated immunity is an immune response that does not involve antibodies, but rather involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen.

Agriculture and Plant virology deals with the cyclic development of  viral disease within plant. Transgenic plants are genetically modified using recombinant DNA technique to create plants with new characteristics. Brome Mosaic Virus- a small icosahedral positive stranded RNA plant virus which is found where wheat and barley is grown. Tobacco-mosaic virus- is a single stranded RNA virus that causes mottling and discolouration of tobacco leaves. Cucumber mosaic virus-are the plant pathogenic virus that occurs in cucumber and tomato plants. Alfalfa mosaic virus- is a phytopathogen that leads to yellow mosaics and necrosis on commercially important crops such as peas, lentils, clovers. Rice Stripe Virus- is a RNA plant pathogen that infects plants such as wheat, corn and rice.

Veterinary virology is the branch of veterinary medicine. It is the study of the viruses in non-human animals. Research in virology and veterinary virology studies the pathogenicity, diagnostic ,identification ,epidemiology and immune responses to a range of viral pathogens for example-Japanese encephalitis virus, HIV, respiratory syncytial virus, cytomegalovirus and other herpes viruses , chicken metapneumovirus, feline calicivirus and Schmallenberg virus. Techniques used include: diagnostic identification methods, flow cytometry, ELISA, epidemiology, PCR and transcriptomic and genomic technologies, including metagenomics, resequencing and genotyping cell separation, proteomics and infection models.

An oncolytic virology is the study of virus that infects and kills cancer cells.They release new infectious virus particles or virions to help destroy the remaining tumour as the infected cancer cells are destroyed by oncolysis.

Microbiology is the study of microscopic organisms, such as bacteria, viruses, archaea, fungi and protozoa. This discipline includes fundamental research on the biochemistry, physiology, cell biology, ecology, evolution and clinical aspects of microorganisms, including the host response to these agents.

Fungi are everywhere. There are approximately 1.5 million different species of fungi on Earth, but only about 300 of those are known to make people sick. Fungal diseases are often caused by fungi that are common in the environment. Fungi live outdoors in soil and on plants and trees as well as on many indoor surfaces and on human skin. Most fungi are not dangerous, but some types can be harmful to health.

Fungal infections are common in humans and are usually not very serious if they are treated quickly and correctly. Anyone with a weakened immune system may be more likely to contract a fungal infection, as well as anyone who is taking antibiotics.

Bacterial and viral infections have many things in common. Both types of infections are caused by microbes -- bacteria and viruses, respectively -- and spread by things such as Coughing and sneezing, Contact with infected people, Contact with contaminated surfaces, food, and water,Contact with infected creatures, including pets, livestock, and insects such as fleas and ticks.

A parasitic disease, also known as parasitosis, is an infectious disease caused or transmitted by a parasite. Many parasites do not cause diseases. Parasitic diseases can affect practically all living organisms, including plants and mammals. The study of parasitic diseases is called parasitology.

Current research in virology includes the investigation of mechanism of HIV replication and pathogenesis .Diseases such as prion diseases, Alzheimer's disease and HIV-1-associated dementia. Other research involves chronic and latent infections caused by viruses such as Epstein-Barr and Kaposi's sarcoma associated herpes virus and herpes simplex. Researcher are also studying viral host interactions along with the mechanism of viral induced cellular transformation.