Advances in Virus Research

Viruses have been around since the beginning of time. They are small organisms that infect cells and replicate themselves using the host's cellular machinery. Most viruses cause disease in humans and animals, but some are harmless. In fact, many viruses are responsible for producing food we eat.  There are two types of viruses: DNA and RNA. DNA viruses are those that use DNA as their genetic material. These viruses are often called "parasites." Examples of these viruses include herpes simplex virus (HSV), human papilloma virus (HPV), adenovirus, and cytomegalovirus (CMV). RNA viruses are those that use RNA as their genetic material. Examples of these viruses include influenza virus, vesicular stomatitis virus (VSV), poliovirus, rhinovirus, and foot-and-mouth disease virus (FMDV).

A virus is a microscopic particle composed of nucleic acid surrounded by protein. Nucleic acid contains the information necessary to make copies of the virus. Protein helps protect the viral nucleic acid from damage.  When a virus enters a cell, it attaches to receptors on the surface of the cell membrane. Once attached, the virus injects its genetic material into the cell where it replicates. Replication means making copies of the virus. The virus then moves out of the cell and may travel to other cells.

 Viral infections can be mild or severe depending on the type of virus involved. Mild infections produce no symptoms. Severe infections result in death.  Vaccines are medicines that prevent people from getting sick. They work by stimulating the immune system to recognize and fight off harmful bacteria and viruses before they become infectious.  Antiviral drugs are medications that treat viral infections. They work by interfering with the replication cycle of the virus.  Viruses can be classified based on how they enter the body. Respiratory viruses enter through the nose or mouth. Gastrointestinal viruses enter through the digestive tract. Genital viruses enter through the genital tract. Herpes viruses enter through the skin. Herpes viruses are a group of double stranded DNA viruses. HSV is the best known member of the herpes family. It causes cold sores and fever blisters. Other members of the herpes family include Epstein-Barr virus (EBV) and varicella zoster virus (VZV).

Human immunodeficiency virus (HIV) is a retrovirus. Retroviruses are a class of viruses that use reverse transcriptase to convert their RNA genome into DNA. HIV uses reverse transcriptase to convert its RNA genome into DNA. After entering the body, the virus travels to the lymph nodes and multiplies. The virus then spreads throughout the body.  Hepatitis B virus (HBV) is a hepadnavirus. Hepadnaviruses are a class that includes hepatitis C virus (HCV). HCV is a single strand RNA virus that replicates through an enzyme called NS5A. HBV is a double stranded DNA virus that replicates through enzymes called polymerases.