Although many viruses do not cause disease or harm, some viruses can attack cells and multiply, causing an infection within the body, according to Dr. Ananya Mandal with News Medical. The harmful effects of viruses can result in a cold, influenza or diseases such as polio, hepatitis or HPV warts.
Viruses typically attack a particular area of the body, according to Mandal. For example, viruses that affect the skin often result in warts, also known as HPV. Respiratory viruses can induce rubella, the measles, mumps, influenza and the common cold. Oral viruses may result in a patient contracting rotavirus, polio, echo, Hepatitis A or coxsackie.
An additional harmful effect of a virus may result in sexually transmitted diseases, such as herpes 1 and 2, HIV or Hepatitis B, according to Mandal. Viruses that result from insect vectors or animal bites often lead to rabies, yellow fever and dengue fever.
Although some viral infections are killed by the host, some virus-infected cells persist and spread to other cells, which causes the virus to reappear within the patient, according to Mandal. The body initially fights the virus if the immune system is strong and provides a protective layer against the virus. When symptoms persist, viruses are typically treated with antibiotics as prescribed by a physician.