The kinds of viruses that can cause childhood rashes probably number in the hundreds. One group alone, the enteroviruses, has about 50 members that have been associated with skin lesions. In the early 1900s the causes of the common childhood rashes were largely unknown, and it was common practice to number them 1 to 6 as follows: (1) rubeola, (2) scarlet fever,
(3) rubella, (4) Duke's disease—a mild disease with fever and bright red generalized rash, now thought to have been due to an enterovirus, (5) erythema infectiosum, and (6) exanthem subitum. The causes of two common childhood rashes, erythema infectiosum and exanthem subitum, have only been established in recent years.
Fifth disease (erythema infectiosum) occurs in both children and young adults. The illness begins with fever, malaise, and
Nester-Anderson-Roberts: I IV. Infectious Diseases I 22. Skin Infections I I © The McGraw-Hill
Microbiology, A Human Companies, 2003
Perspective, Fourth Edition
Table 22.11 German Measles (Rubella)
© Airborne rubella virus infects nose and throat.
© Virus taken up by lymph nodes in the region.
© Rubella virus multiplies and enters the bloodstream.
@ Circulating virus reacts with antibodies, resulting in antibody-antigen complexes.
© Antibody-antigen complexes lodge in the skin, causing a rash and pain in the joints.
© In women during pregnancy, rubella virus crosses the placenta, infecting the fetus, resulting in congenital rubella syndrome.
@ Transmission to others by respiratory secretions.
22.4 Skin Diseases Caused by Viruses 555
Symptoms Mild fever and cold symptoms, rash beginning on forehead and face, enlarged lymph nodes behind the ears
Incubation period 14 to 21 days
Causative agent Rubella virus, an RNA virus of the togavirus family
Pathogenesis Following replication in the upper respiratory tract, virus disseminates to all parts of the body and crosses the placenta; surviving fetuses often develop abnormally, and they excrete the virus for months after birth
Epidemiology Virus possibly present in nose and throat from 1 week before rash to 1 week after; infection occurs via the respiratory route; humans are the only source
Prevention and Attenuated rubella virus treatment vaccine administered to children at 12 to 16 months, repeated at 4 to 6 years of age. No specific antiviral treatment head and muscle aches. A diffuse redness appears on the cheeks, giving the appearance of the face as if it were slapped. The rash commonly spreads in a lacy pattern to involve other parts of the body, especially the extremities. The rash may come and go for 2 weeks or more before recovery. Joint pains are a prominent feature of some adult infections. The disease is caused by parvovirus B-19, a small (18-28 nm), non-enveloped, single-stranded DNA virus of the parvovirus family. The virus preferentially infects certain bone marrow cells and is a major threat to persons with sickle cell and other anemias because the infected marrow sometimes stops producing blood cells, a condition known as aplastic crisis. Also, about 10% of women infected with the virus during pregnancy suffer spontaneous abortion.
Roseola (exanthem subitum, roseola infantum), is a common disease in infants six months to three years old. It causes a great deal of parental anxiety because it begins abruptly with fever that may reach 105 °F and cause convulsions. The children generally do not appear ill, however. After several days, the fever vanishes and a transitory red rash appears, mainly on the chest and abdomen. The patient has no symptoms at this point, and the rash vanishes in a few hours to 2 days. This disease is caused by herpesvirus, type 6. There is no vaccine against the disease, and no treatment except to reduce the risk of seizures by sponging with lukewarm water and using medication to keep the temperature below 102°F.
Papillomaviruses, cause of warts, can infect the skin through minor abrasions. Warts are small tumors called papillomas that consist of multiple nipplelike protrusions of tissue covered by skin or mucous membrane. Warts rarely become cancers, although some sexually
Figure 22.25 Wart Virus The virions appear yellow in this color-enhanced transmission electron micrograph.
transmitted papillomaviruses are strongly associated with cervical cancer. About 50% of the time, warts on the skin disappear within 2 years without any treatment. Papillomaviruses (figure 22.25) belong to the papovavirus family. They are small (about 50 nm diameter), non-enveloped, double-stranded DNA viruses. More than 50 different papillomaviruses are known to infect humans. Warts of other animals are generally not infectious for humans.
Papillomaviruses have been very difficult to study because they fail to grow in cell cultures or experimental animals. Wart viruses can survive on inanimate objects such as wrestling mats, towels, and shower floors, and infection can be acquired from such contaminated objects. The virus infects the deeper cells of the epidermis and reproduces in the nuclei. Some of the infected cells grow abnormally and produce the wart. The incubation period ranges from 2 to 18 months. Infectious virus is present in the wart and can contaminate fingers or objects that pick or rub the lesions. Like other tumors, warts can only be treated effectively by killing or removing all of the abnormal cells. This can usually be accomplished by freezing the wart with liquid nitrogen, by cauterization, meaning burning the tissue usually with an electrically heated needle, or by surgical removal. Virus generally remains in the adjacent normal-appearing skin, however, and may cause additional warts. Warts that grow on the soles of the feet are called plantar warts (often mistakenly called planter's warts; plantar is a word meaning "referring to the sole of the foot"). These warts are very difficult to get rid of because the pressure of standing on them causes them to grow wide and deep. ■ cervical cancer, p. 754
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