Rubella and Rubeola Infections



Rubella and Rubeola Infections



Learning Objectives


At the conclusion of this chapter, the reader should be able to:


• Describe the etiology and epidemiology of rubella (German measles) infection.


• Explain the signs and symptoms of acquired and congenital rubella infection.


• Compare the immunologic manifestations of acquired and congenital rubella infection.


• Explain the laboratory diagnostic evaluation of rubella infection.


• Summarize the epidemiology and laboratory diagnosis of rubeola (measles).


• Analyze a representative case study.


• Correctly answer case study related multiple choice questions.


• Be prepared to participate in a discussion of critical thinking questions.


• Describe the principle, results, limitations, and clinical applications of the passive latex agglutination test for Rubella.


• Correctly answer end of chapter review questions.



Key Terms




Rubella


Etiology of Rubella


The rubella virus was first isolated in 1962. Acquired rubella, also known as German measles or 3-day measles, is caused by an enveloped, single-stranded RNA virus of the Togaviridae family. Because the virus is endemic to human beings, the disease is highly contagious and is transmitted through respiratory secretions. Before widespread rubella immunization, this viral infection usually occurred in childhood, although it also affected adults.



Epidemiology of Rubella


Three strains of live, attenuated rubella vaccine virus were developed and first licensed for use in the United States in 1969. Before widespread rubella immunization in the United States and Canada, rubella infections occurred in epidemic proportion at 6- to 9-year intervals. In 1964, more than 20,000 cases of congenital rubella syndrome and an unknown number of stillbirths occurred in the United States as the result of an epidemic that year.


The Pan American Health Organization (PAHO) has made historic achievements in the elimination of measles (rubeola) and has announced a new effort to eliminate (rubella) German Measles. Many countries in the regions of the Americas have already made great progress in reducing the incidence of congenital rubella syndrome (CRS) through accelerated rubella control programs. Costa Rica, Honduras, Brazil, and Chile, as well as the member countries of the Caribbean, have rubella elimination initiatives underway.


In countries where vaccination is uncommon, the incidence of rubella infection is high and epidemics are frequent. Because vaccination programs have prevented the rubella epidemics that once gave people naturally acquired immunity, individuals who have not been vaccinated have a higher level of susceptibility to rubella infection. Primarily, two types of outbreaks have occurred in the United States in the fairly recent past, affecting the following groups:



The epidemiology of measles reveals two major impediments to measles elimination: (1) unvaccinated preschool-age children, a factor that allows large outbreaks; and (2) vaccine failures, which account for outbreaks in highly vaccinated school-age populations. On U.S. college and university campuses, the susceptibility to rubella infection among students is estimated to be as high as 20%. Many cases of rubella infection have been unrecognized or unreported because these cases are mild or subclinical.


Contracting the infection and vaccinating against rubella are the only routes to developing immunity. Individuals should be immune to rubella if they have a dated record of rubella vaccination on or after their first birthday, or if they have demonstrable rubella antibody. Even when antibody titers fall to relatively low levels, previous infection or successful vaccination appears to confer permanent immunity to rubella, except in cases of congenital rubella. The only proof of immunity is a positive serologic screening test result for rubella antibody. A history of rubella infection, even if verified by a physician, is not acceptable evidence of immunity.


It is critical to continue to determine the rubella immune status of women of childbearing age and to vaccinate those who are not immune. Individuals requiring rubella immune status determination include those in the following groups:



If the woman is not rubella immune, she should be vaccinated and advised not to become pregnant for 3 months because of the remote possibility that the vaccination could lead to an infected fetus.



A positive test confirms immunity, but to rule out any possibility of unsuspected current infection, an immunoglobulin M (IgM) screening procedure may also be ordered. If the patient is not rubella-immune, she should be cautioned to avoid exposure to rubella infection. Vaccination is contraindicated in pregnant women; however, a woman should be vaccinated immediately after termination of the pregnancy.



Men and women should be vaccinated to prevent possible spread of nosocomial infection to pregnant patients.


Adverse reactions to rubella vaccine have been reported. The Institute of Medicine has determined that a causal relationship exists between rubella vaccine and acute arthritis in adult females. There is weak but consistent evidence for a causal relationship between rubella vaccine and chronic arthritis in adult females. Incidence rates are estimated to average 13% to 15% in adult females after vaccination. Much lower levels of arthritic adverse reactions were noted in children, adolescents, and adult males. Reliable estimates of excess risk of chronic arthritis after rubella vaccination are not available.



Signs and Symptoms of Rubella Infection


A diagnosis of acquired rubella is not based solely on clinical manifestations. The signs and symptoms of rubella vary widely from person to person and may not be recognized in some cases, especially if the characteristic rash is light or absent, as may occur in a substantial number of cases. Rubella infection also may resemble other disorders, such as infectious mononucleosis and drug-induced rashes.



Acquired Rubella Infection


The incubation period of acquired rubella infection varies from 10 to 21 days, and 12 to 14 days is typical. Infected persons are usually contagious for 12 to 15 days, beginning 5 to 7 days before the appearance (if present) of a rash. Acute rubella infection lasts from 3 to 5 days and generally requires minimal treatment. Permanent effects are extremely rare in acquired infections.


The clinical presentation of acquired rubella is usually mild. The clinical manifestations of infection usually begin with a prodromal period of catarrhal symptoms, followed by involvement of the retroauricular, posterior cervical, and postoccipital lymph nodes, and finally by the emergence of a maculopapular rash on the face and then on the neck and trunk (Figs. 24-1 and 24-2). A temperature less than 34.4° C (94° F) is usually present. In older children and adults, self-limiting arthralgia and arthritis are common.


image
Figure 24-1 Rubella. (From Odom RB, James WD, Berger TG: Andrews’ diseases of the skin: clinical dermatology, ed 9, St Louis, 2000, Saunders.)

image
Figure 24-2 Rubella rash. (From Krugman S et al: Infectious diseases of children, ed 8, St Louis, 1985, Mosby.)


Congenital Rubella Infection


Rubella infection is usually a mild, self-limiting disease with only rare complications in children and adults. In pregnant women, however, especially those infected in the first trimester, rubella can have devastating effects on the fetus (Fig. 24-3). In utero infection can result in fetal death or manifest as rubella syndrome, a spectrum of congenital defects. About 10% to 20% of infants infected in utero fail to survive beyond 18 months.


image
Figure 24-3 Congenital malformations of rubella. (From Krugman S et al: Infectious diseases of children, ed 8, St Louis, 1985, Mosby.)

The point in the gestation cycle at which maternal rubella infection occurs greatly influences the severity of congenital rubella syndrome (Table 24-1); the extent of congenital anomalies varies from one infant to another. Some infants manifest almost all the defects associated with rubella, whereas others exhibit few, if any, consequences of infection. Clinical evidence of congenital rubella infection may not be recognized for months or even years after birth.



Table 24-1


Manifestation of Anomalies in Maternal Rubella



























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Jun 12, 2016 | Posted by in IMMUNOLOGY | Comments Off on Rubella and Rubeola Infections

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Period of Gestation Risk of Anomaly
Prospective Studies
First trimester ≈25%
Second trimester  
First month Less than (>)1%
Second month ≥25%
Third month ≥10%
Serologically Confirmed Cases of Maternal Infection