Essentials of Anatomy and Physiology

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Table 22–4 DISEASES CAUSED BY VIRUSES (Continued)

Virus Discussion/Disease(s) Caused

Rubella virus

Parvovirus B19

Mumps virus

Polio viruses

Coxsackie viruses

(29 types)

Rabies virus

Encephalitis

viruses

West Nile virus

Dengue virus

(4 serotypes)

Rotaviruses

Norwalk viruses

Ebola viruses

Marburg virus

Yellow fever virus

German measles: mild upper respiratory symptoms; a rash may or may not be present. The virus

may cross the placenta and cause congenital rubella syndrome (CRS): blindness, deafness,

heart defects, mental retardation, or miscarriage. CRS is most likely to occur if the fetus is

infected during the first trimester. The vaccine is given to infants (MMR).

Fifth disease: a childhood illness characterized by a rash on the cheeks and limbs. Adults may

develop transitory arthritis; anemia may occur in immunocompromised people or those with

sickle-cell anemia. The virus can cross the placenta and may cause miscarriage or severe dam-

age to the fetal liver. No vaccine yet for human disease (as there are for animal parvoviruses)

because development of one is not seen as commercially profitable.

Mumps: fever, swelling of the parotid salivary glands and perhaps the others (asymptomatic

infections do occur); the virus is spread in saliva. Complications are rare in children but

include pancreatitis, nerve deafness, and mumps encephalitis. Adult men may develop orchi-

tis, inflammation of the testes. Adult women may develop oophoritis, inflammation of the

ovaries. The vaccine is given to infants.

Polio: most infections are asymptomatic or mild; major infection may result in paralysis. Two vac-

cines: IPV (Salk) contains a killed virus and cannot cause polio; booster injections are needed.

OPV (Sabin) contains an attenuated virus, is given orally, and carries a very small risk of caus-

ing polio. In the U.S., polio cases are vaccine related; polio is still endemic in other parts of

the world. The WHO has set 2007 as the revised goal for the eradication of polio.

Hand, foot, and mouth disease: fever, blisters on the palms, soles, tongue, and throat; most com-

mon among children. May also cause conjunctivitis, myositis, and myocarditis. Highly conta-

gious, spread by the fecal–oral route and by respiratory droplets. No vaccine.

Rabies: headache, nausea, fever, spasms of the swallowing muscles; seizures; fatal because of

respiratory or heart failure; virtually 100% fatal. Reservoirs are wild animals; the virus is pres-

ent in their saliva. Post-exposure prevention requires Human Rabies Immune Globulin (HRIG-

antibodies) and the rabies vaccine.

Encephalitis: most infections are mild; CNS involvement is indicated by confusion, lethargy, or

coma. Several types of these viruses occur in the U.S. Reservoirs are wild birds and small

mammals; vectors are mosquitoes. Vaccines are available for horses and for people whose

occupations put them at risk.

West Nile encephalitis: first found in North America in New York City in 1999 (well known in

Africa and the Middle East). Natural reservoirs are birds; several species of mosquitoes are vec-

tors. Symptoms include headache and confusion, but most infections are mild or asympto-

matic; fatalities are not common. No vaccine.

Dengue fever: an influenza-like illness (break-bone fever), and dengue hemorrhagic fever charac-

terized by vascular leakage and defective clotting. Vectors are species of mosquitos in the

genusAedes. Endemic in the tropics and subtropics, with an estimated 100 million cases per

year and 25,000 fatalities, and is moving north. Vaccines are in the testing stages.

Enteritis: worldwide the leading cause of diarrhea and potentially fatal dehydration in infants and

children. Two vaccines have passed clinical tests.

Gastroenteritis: vomiting; called by many “stomach flu.” Acquired from food such as shellfish, or

from food handled by people with mild cases. No vaccine.

Hemorrhagic fever: high fever, systemic hemorrhages, necrosis of the liver; mortality rate

25%–90%. The viruses also affect monkeys, which may be reservoirs of infection. Vaccines are

in the testing stage.

Hemorrhagic fever similar to that caused by Ebola virus. A vaccine is in the testing stage.

Yellow fever: hemorrhages in the liver, spleen, kidneys, and other organs. The vector is a mos-

quito. The vaccine is recommended for travelers to endemic areas: Central and South America

and Africa.