COMMON VIRAL INFECTION, Summaries of Biology

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C O M M O N

V I R A L A N D

IN F ECTION S

V I R A L

INFECTION

O F THE S K I N

C H I C K E N P O X A N D

S H I N G L E S

Shingles (also known as herpes zoster) is a reactivation of the varicella virus, often the result of immunosuppression. Shingles involves inflammation of sensory ganglia of cutaneous sensory nerves, producing fluid-filled blisters, pain, and paresthesia (numbness and tingling). Shingles may occur at any age, but is most common after age 50. Patient Care. Use Airborne and Contact Precautions for hospitalized patients until their lesions become dry and crusted.

SHINGLES

02

PATHOGEN Chickenpox and shingles are caused by varicella-zoster virus (VZV); a herpes virus (family Herpesviridae) that is also known as human herpesvirus 3; a DNA virus. RESERVOIRS AND MODE OF TRANSMISSION Infected humans serve as reservoirs. Transmission is from person to per- son by direct contact or droplet or airborne spread of vesicle fluid or secretions of the respiratory system of persons with chickenpox. PATIENT CARE Use Airborne and Contact Precautions for hospitalized patients until their lesions become dry and crusted.

S H I N G L E S S Y M P T O M S

Headache Chills Upset stomach

German measles is a mild, febrile viral

disease. A fine, pinkish, flat rash begins 1 or 2

days after the onset of symptoms. The rash

starts on the face and neck and spreads to

the trunk, arms, and legs. Rubella is a milder

disease than hard measles with fewer

complications. If acquired dur- ing the first

trimester of pregnancy, rubella may cause

congenital rubella syndrome in the fetus. This

can lead to intrauterine death, spontaneous

abortion, or congenital malformations of

major organ systems.

G E R M A N M E A S L E S

(RUBELLA)

M E A S L E S

Hard Measles, Rubeola). Measles is an acute, highly communicable viral disease with fever, conjunc- tivitis, cough, photosensitivity (light sensitivity), Koplik spots in the mouth, and red blotchy skin rash. Koplik spots are small red spots, in the center of which can be seen a minute bluish white speck when observed under a strong light. The rash begins on the face between days 3 and 7 and then becomes generalized. Complications include bronchitis, pneumonia, otitis media, and encephalitis. Rarely, autoimmune, subacute, sclerosing panencephalitis (SSPE) may follow a latent period of several years. SSPE is characterized by gradual progressive psychoneurological deterioration, including personality changes, seizures, photosensitivity, ocular abnormalities, and coma.

PATHOGEN Measles is caused by measles virus (also known as rubeola virus). It is an RNA virus in the family Paramyxoviridae. RESERVOIRS AND MODE OF TRANSMISSION Infected humans serve as reservoirs. Airborne transmission occurs by droplet spread, direct contact with nasal or throat secretions of infected persons, or with articles freshly soiled with nose and throat secretions. PATIENT CARE Use Airborne Precautions for hospitalized patients until 4 days after the onset of rash.

Smallpox is a 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.

S M A L L P O X

PATHOGEN Smallpox is caused by two strains of variola virus: variola minor (with a fatality rate of < 1 %), and variola major (with a fatality rate of 20 %- 40 % or higher). Variola virus is a double-stranded DNA virus in the genus Orthopoxvirus, family Poxviridae. Smallpox virus is a potential biological warfare and bioterrorism agent. RESERVOIRS AND MODE OF TRANSMISSION Before smallpox was eradicated, infected humans were the only source of the virus. There are no known animal or environ- mental reservoirs. Person-to-person transmission is via the respiratory tract (droplet spread) or skin inocu lation. Patients are most contagious before eruption of the rash, by aerosol droplets from oropharyngeal lesions. PATIENT CARE Use Airborne and Contact Precautions for hospitalized patients until all scabs have crusted and separated (3- 4 weeks). Use N95 or higher respiratory protection.

W A R T S

Warts consist of 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. Venereal or genital warts are discussed in more detail later in the chapter

PATHOGEN Warts are caused by at least 70 types of human papillomaviruses (HPV). They are classified in the genus Papillomavirus within the family Papovaviridae. They are DNA viruses. RESERVOIRS AND MODE OF TRANSMISSION

. Infected humans serve as reservoirs. Transmission usually occurs by direct contact. Genital warts are sexually transmitted. They are easily spread from one area of the body to another, but most are not very contagious from person to person (genital warts are an exception).

V I R A L

INFECTION

O F THE E Y E

A D E N O V I R A L

CONJUNCTIVITIS A N D

KERATOCONJUNCTIVITIS

These are acute viral diseases of one or both eyes, associated with inflammation of the conjunctiva, edema eyelid and periorbital tissue, pain, photophobia, and blurred vision. The cornea is involved in about 50% of cases, with permanent scarring of the cornea in severe cases.