Types of viral infection
Many virus infections are not easily treatable because the virus is protected within the host cell. In many cases symptoms are unpleasant but not life-threatening and the virus is usually eliminated by the body’s immune system, however, others can be more serious. Example of virus infections include:
- The common cold caused by inhaled rhinovirus, resulting in infection of the upper respiratory tract, with symptoms including inflammation, irritation of the throat and nasal passages and rhinitis (runny nose).
- Influenza or flu, caused by inhaling droplets containing live particles of the virus hemophilus Influenza that infects the upper respiratory tract. It is often confused with a cold but the symptoms are much more severe and can be deadly. The influenza virus exists as different strains and these strains mutate regularly. However, a flu vaccine has been developed, which helps stimulate the body’s immune system to fight infection with the flu virus.
- Human Papillomavirus (HPV) infects skin cells by direct skin to skin contact, causing warts, which are non-cancerous overgrowth of outer layers of skin around the infected cells. Genital warts are a sexually transmitted condition with symptoms including pain, bleeding and itching. Common skin warts usually form as raised bumps on the hands and feet, also elbows and knees. Warts on the underside of the foot are known as verrucae and can be painful as they grow into the foot.
- Herpes Simplex Virus (HSV) infects mucous membrane cells of the lips (HSV I) and genitals (HSV-II) forming blisters that crust over to form a scab as they heal. Varicella zoster virus, a Herpes-like virus, causes chicken pox and also and shingles (herpes zoster).
- Human immunodeficiency virus (HIV) infects specific cells of the immune system and can cause Acquired Immunodeficiency Syndrome (AIDS), which results in a compromised immune system and increased risk of opportunistic infections.
- Some viruses become latent and are reactivated later. For example Herpes virus lies dormant in nerve cells of the skin and then travels back up the nerve to cause more blisters. Similarly Varicella virus can cause shingles if reactivated. Periods of disease remission following HIV infection are also due to viral latency and once infected with HPV, warts can disappear and reappear indefinitely.
Types of antiviral medication Medications available to treat viral infections include:
- Imiquimod, used as a topical treatment for genital warts and acts as an immunomodifier by stimulating immune cells in the outer skin layers to produce chemicals called cytokines involved in fighting invasion by HPV.
- Podophyllotoxin, a plant extract that is used as a topical treatment for genital warts and works by killing skin cells infected with HPV.
- Oseltamivir, used as a treatment for influenza types A and B and works by inhibiting an important viral enzyme, neuraminidase that is needed for the influenza virus to be able to enter and infect a host cell and then to allow new virus to be released from the infected cell.
- Acyclovir, used to treat infection with HSV-I that causes cold sores, and HSV-II that causes genital herpes. It is also used to treat shingles or herpes zoster caused by varicella virus. It is a nucleoside analogue and becomes incorporated into the viral DNA within the host cell, which blocks the action of viral DNA polymerase needed for viral DNA synthesis, without affecting normal cellular processes. Acyclovir is available for oral or topical treatment. Valacyclovir is a prodrug of acyclovir that is more readily absorbed and is converted to acyclovir by the liver.