Viral Infections

Influenza, also called the flu, is a highly contagious viral infection that affects the nose, throat, and lungs. This virus is seasonal and more prevalent from fall to spring. Influenza has three antigen types: A, B, and C. Influenza A causes a moderate to severe infection. Influenza B usually causes mild illness in children. Influenza C is very rare in humans. This viral infection is transmitted easily via contaminated droplets during coughing, sneezing, or talking. Droplets enter into the respiratory tract of the unaffected person and begin replication 24 hours before the appearance of symptoms. Usually influenza has an abrupt onset with the first symptoms being high fever, headache, fatigue, and myalgia (muscle aches). A sore throat, nonproductive cough, watery nasal discharge, weakness, red watery eyes, chills, and photophobia may also occur.

Herpesviruses are large viruses that cause infections. Among the most familiar are herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2); varicella-zoster viruses (HSV-3 or VZV), more commonly known as chickenpox and shingles; Epstein-Barr virus (HSV-4 or EBV); and cytomegalovirus (HHV-5 or CMV). HSV-1 is usually associated with cold sores (vesicular lesions), which grow in neurons. The HSV-1 virus is capable of latency (ability to maintain disease potential without signs and symptoms). HSV-2 is usually associated with vesicular lesions and small ulcerations on the genitalia (genital herpes). The HSV-2 virus remains dormant by traveling through the peripheral nerves to the sacral dorsal root ganglia. The virus can be transported back the nerve root to the skin for reactivation at any time. While dormant, the virus continues to replicate. Both HSV-1 and HSV-2 are capable of causing recurrent infections. Both viruses can replicate in the mucous membranes and skin of the oropharynx or genitalia. The virus is transmitted by contact with infectious lesions or secretions. HSV-1 is spread by oral secretions from one individual to another. From the mouth, this virus can spread to the genital area by oral intercourse or poor hand washing. HSV-2 is usually spread by intimate sexual contact, or an infected mother can transmit the virus to her infant during childbirth. When signs and symptoms are present, they usually include eruption of small pustules and vesicles; fever; headache; malaise; myalgia; as well as tingling, itching, and pain in the genital area.

The varicella zoster virus (VZV or HSV-3) causes chickenpox and shingles. Chickenpox is a highly contagious viral infection that causes generalized pruritic vesicles and fever. It has become less common since a vaccine was developed; however, some outbreaks still occur. Shingles is a painful vesicular rash that can remain dormant in nerve cells. When a person who has previously been infected with chickenpox becomes older or develops a weakened immune system, the VZV can reactivate causing an outbreak along the region of skin innervated by the nerve where the virus resides. In addition to the rash, the patient may also develop fever, malaise, and myalgia.

Epstein-Barr virus (EBV or HSV-4) most commonly causes infectious mononucleosis, a condition manifested by fever, tonsillitis, and enlarged lymph nodes in the neck. EBV resides in lymphocytes, epithelial cells, and muscle cells and has a latency period.

Cytomegalovirus (CMV or HHV-5) is a very common infectious disease worldwide. It is thought that most adults have had this viral infection at one time and are unaware. Most individuals do not require treatment for CMV unless they are immunocompromised (e.g., babies or individuals who have had organ transplantations). CMV is transmitted via body fluids, especially saliva or urine; by kissing, sexual contact, or sharing food; or by a pregnant patient to the fetus. In susceptible individuals, CMV infection can lead to fatal pneumonia or blindness (due to an infected retina).

Hepatitis B (HBV) is a serious liver infection caused by the hepatitis B virus. The transmission of HBV is usually via a needlestick, intimate sexual contact, or childbirth. HBV is found in all body fluids, including blood, semen, and vaginal fluid. The signs and symptoms of HBV include anorexia, vomiting, diarrhea, jaundice, malaise, and myalgia.

A viral infection usually can be detected only after the virus has replicated itself. Viruses can cause mild to severe infections. General signs and symptoms of an acute viral infection include headache, low-grade fever (with a mild viral infection), nausea, vomiting, diarrhea, muscular pain, fatigue, and cough.