1.1

• It would be impossible in a book of this size to describe all of the human infectious diseases caused by viruses. Thus, only selected viral diseases are described in this chapter.
• Certain of the viral diseases described in this chapter are nationally notifiable infectious diseases; that is, when a patient is diagnosed with one of these diseases in the United States, the information must be reported to the Centers for Disease Control and Prevention.
• As of 2017, there were approximately 25 nationally notifiable viral diseases (see Table 18-1). Most of them are described in this chapter, as are some viral diseases that are not nationally notifiable.
• Viruses


  Can infect only the cells bearing appropriate surface receptors (i.e., surface receptors that the virus is able to recognize and bind to)
• Viruses are specific as to the type of cell(s) that they can infect. For this reason, certain viruses cause only respiratory infections, whereas others cause only gastrointestinal infections, and so on.
• Viruses multiply within host cells, and it is during their escape from those cells-by either cell lysis or budding-that the host cells are destroyed. This cell destruction leads to most of the symptoms of the viral infection, which vary depending on the location of the infection.
• Other symptoms are the result of immunologic injury (i.e., injury that results from the immune response to the viral pathogen).
• In the case of the acquired immunodeficiency syndrome (AIDS) virus (human immunodeficiency virus [HIV]), the virus destroys cells of the immune system. This renders the patient unable to ward off various viral, bacterial, fungal, and parasitic pathogens. The death of AIDS patient results from overwhelming infections caused by these pathogens.
• Viral infections of the skin

  • Chickenpox and shingles
  • German measles (rubella)
  • Hand, foot, and mouth disease (HFMD)
  • Measles (hard measles, rubeola)
  • Smallpox
  • Warts
• Chickenpox (varicella)


  Acute, generalized viral infection, with fever and a skin rash. Vesicles also form in mucous membranes. It is usually a mild, self-limiting disease, but can be severely damaging to a fetus. Serious complications include pneumonia, secondary bacterial infections, hemorrhagic complications, and encephalitis.
• Shingles (herpes zoster)


  Reactivation of the varicella virus, often the result of immunosuppression. Involves inflammation of sensory ganglia of cutaneous sensory nerves, producing fluid-filled blisters, pain, and paresthesia (numbness and tingling).
• German measles (rubella)


  Mild, febrile viral disease. A fine, pinkish, flat rash begins 1 or 2 days after the onset of symptoms. If acquired during the first trimester of pregnancy, rubella may cause congenital rubella syndrome in the fetus.
• Hand, foot, and mouth disease (HFMD)


  Common viral illness that usually affects infants and children younger than 5 years. Starts with a fever, sore throat, and malaise. One or two days after the fever starts, painful sores can develop in the mouth. A skin rash with red spots may also develop over the next few days on the palms of the hands and soles of the feet.
• Measles (hard measles, rubeola)

  Acute, highly communicable viral disease with fever, conjunctivitis, cough, photosensitivity (light sensitivity), Koplik spots in the mouth, and red blotchy skin rash. Complications include bronchitis, pneumonia, otitis media, and encephalitis. Rarely, autoimmune, subacute, sclerosing panencephalitis (SSPE) may follow a latent period of several years.
• Smallpox


  Systemic viral infection with fever, malaise, headache, prostration, severe backache, a characteristic skin rash, and occasional abdominal pain and vomiting. The rash is similar to, and must be distinguished from, the rash of chickenpox. Smallpox can become severe, with bleeding into the skin and mucous membranes, followed by death.
• Warts


  Many varieties of skin and mucous membrane lesions, including common warts (verrucae vulgaris), venereal warts, and plantar warts. Most are harmless, but some can become cancerous.
• The most common viruses detected in middle ear fluid are respiratory syncytial virus (RSV), rhinovirus/enterovirus, influenza viruses, human metapneumovirus, and adenoviruses.
• Keratitis


  Infection of the cornea
• Keratitis


  • Commonly caused by herpes simplex virus (HSV)
  • Other viruses can also cause it
• Conjunctivitis


  Infection of the conjunctiva
• Conjunctivitis


  • Can have viral and bacterial etiologies
  • Can be noninfectious in nature
• Keratoconjunctivitis


  Simultaneous infection of the cornea and conjunctiva
• Treatment of ocular viral infections

  Often includes topical eye drops with various antiviral agents
• Viral infections of the eyes

  • Conjunctivitis
  • Keratitis
  • Keratoconjunctivitis
• Conjunctivitis, keratitis, and keratoconjunctivitis

  • Acute viral diseases of one or both eyes
  • Associated with inflammation of the conjunctiva, edema of the eyelids and periorbital tissue, pain, photophobia, and blurred vision
  • Keratitis can result in permanent scarring of the cornea in severe cases
• Patient care for ocular viral infections


  Use Contact Precautions for hospitalized patients for the duration of the illness
• Hemorrhagic conjunctivitis


  • Viral disease with sudden onset, redness, swelling, and pain in one or both eyes
  • Small, discrete subconjunctival hemorrhages may enlarge to form confluent subconjunctival hemorrhages
• Pharyngoconjunctival fever


  Adenoviral syndrome characterized by upper respiratory disease, fever, and minor degrees of corneal epithelial inflammation
• Uveitis and retinitis


  • Inflammation of the eye with many manifestations depending on the site of the infection
  • Infections may result in loss of vision acuity or even blindness
  • Diagnosis is by ophthalmologic examination
• Pathogens for ocular viral infections

  • Adenoviruses cause conjunctivitis and keratoconjunctivitis
  • Herpes simplex viruses most often cause keratitis but can also cause keratoconjunctivitis
• Reservoirs and mode of transmission for ocular viral infections

  • Infected humans serve as reservoirs
  • Transmission occurs via direct contact with eye secretions or contact with contaminated surfaces, instruments, or solutions
• Laboratory diagnosis of ocular viral infections

  • Diagnosis is made by cell culture, immunodiagnostic, or molecular diagnostic procedures
  • Keratitis is often diagnosed clinically by ophthalmology examination
• Pathogens for hemorrhagic conjunctivitis

  Caused by adenoviruses and enteroviruses
• Reservoirs and mode of transmission for hemorrhagic conjunctivitis

  • Infected humans serve as reservoirs
  • Transmission occurs by direct or indirect contact with discharge from infected eyes
  • Adenovirus transmission may be associated with poorly chlorinated swimming pools
• Laboratory diagnosis of hemorrhagic conjunctivitis

  Diagnosis is made by cell culture, immunodiagnostic, or molecular diagnostic procedures
• Pathogens for uveitis and retinitis


  • Caused by cytomegalovirus, herpes simplex and herpes zoster viruses, West Nile virus, Ebola virus, and Zika virus
  • Bacterial infections such as syphilis and tuberculosis, and fungal infections, can also affect the eye
  • The parasite Toxoplasma gondii is a relatively common cause of uveitis
• Laboratory diagnosis of uveitis and retinitis

  Specimens submitted by the ophthalmologist can be examined by bacterial and fungal culture and molecular diagnostic procedures
• Patient care for viral infections of the lower respiratory tract

  Use Droplet Precautions for hospitalized patients
• Pathogens for the common cold

  • Rhinoviruses, coronaviruses, parainfluenza viruses, RSV, influenza viruses, adenoviruses, and enteroviruses
• Reservoirs and mode of transmission for the common cold

  • Infected humans serve as reservoirs
  • Transmission is via respiratory secretions by way of hands and fomites or direct contact with or inhalation of airborne droplets