Treatment

Drugs that combat viral infections are called antiviral drugs. Many antiviral drugs work by interfering with replication of viruses. Most drugs used to treat human immunodeficiency virus (HIV) infection (see Human Immunodeficiency Virus (HIV) Infection: Treatment) work this way. Because viruses are tiny and replicate inside cells using the cells' own metabolic functions, there are only a limited number of metabolic functions that antiviral drugs can target. In contrast, bacteria are relatively large organisms, commonly reproduce by themselves outside of cells, and have many metabolic functions that antibacterial drugs (antibiotics) can target. Therefore, antiviral drugs are much more difficult to develop than antibacterial drugs. Antiviral drugs can be toxic to human cells. Viruses can develop resistance to antiviral drugs.

Other antiviral drugs strengthen the immune response to the viral infection. These drugs include several types of interferons, immunoglobulins, and vaccines. Interferon drugs are replicas of naturally occurring substances that slow or stop viral replication. Immune globulin is a sterilized solution of antibodies (also called immunoglobulins) collected from a group of people. Vaccines are materials that help prevent infection by stimulating the body's natural defense mechanisms. Many immune globulins and vaccines are given before exposure to a virus to prevent infection. Some immune globulins and some vaccines, such as those for rabies and hepatitis B, are also used after exposure to the virus to help prevent infection from developing or reduce the severity of infection. Immune globulins may also help treat some established infections and also prevent infection after future exposures to the virus.

Most antiviral drugs can be given by mouth. Some can also be given by injection into a vein (intravenously) or muscle (intramuscularly). Some are applied as ointments, creams, or eye drops or are inhaled as a powder.

Antibiotics are not effective against viral infections, but if a person has a bacterial infection in addition to a viral infection, an antibiotic is often necessary.