Introduction
Background
Measles (rubeola) is a highly contagious and potentially serious viral infection, with a characteristic viral prodrome and rash. It was once one of the most common and important infections worldwide, but it has become very rare in developed countries where vaccine use is prevalent. Unfortunately, it is the leading vaccine-preventable cause of child mortality worldwide.
Pathophysiology
Measles is caused by a single-stranded RNA paramyxovirus, which is transmitted by respiratory droplets produced by sneezing and coughing. Humans are the only known reservoir for this viral infection.
The portal of entry for the virus is the respiratory tract and possibly the conjunctivae. After undergoing local replication and spreading to regional lymph nodes, viremia ensues, which results in viral dissemination throughout the body, particularly to the skin and mucous membranes. This results in the characteristic clinical features of the infection.
Frequency
United States
Since 1994, most cases of measles have been imported or importation associated, suggesting that measles is no longer an indigenous disease. In 2005, 66 cases of measles were reported to the Centers for Disease Control and Prevention (CDC).1 Of these, 34 were linked with a single outbreak in Indiana associated with the return of an unvaccinated 17-year-old American traveling in Romania.
From January to June 2008, 131 cases of measles were reported to the CDC compared with an average of 63 cases per year during 2000-2007; this is the highest reported since 1996.2
International
In developing countries, measles affects 30 million children a year and causes 1 million deaths. Measles causes 15,000-60,000 cases of blindness per year.
Mortality/Morbidity
Although measles is a clinically significant viral illness, it is usually benign and uncomplicated. Complications most commonly occur in adults and in children who are undernourished, who have vitamin A deficiency, who have an intense exposure to measles or no previous vaccination, or who are immunocompromised.
Most complications occur because the measles virus suppresses the host's immune responses, resulting in a reactivation of latent infections or superinfection by a bacterial pathogen. Therefore, pneumonia, either due to the measles virus itself, tuberculosis, or another bacterial etiology, is the most frequent complication.
Croup, encephalitis, and pneumonia are the most common causes of death associated with measles.
- The measles virus frequently involves the CNS directly; however, clinically apparent encephalomyelitis occurs in about 1 of every 1000-2000 patients with measles. This condition is fatal in about 10% of patients.
- In children with lymphoid malignant diseases, delayed-acute measles encephalitis may develop 1-6 months after the acute infection and is generally fatal. Even rarer is subacute sclerosing panencephalitis (SSPE), a disease with a latent period of several years in children who had measles when they were younger than 2 years.
- Other complications are otitis media, thrombocytopenia with purpura and bleeding, myocarditis, hepatitis, pericarditis, and severe keratitis that may progress to blindness.
Sex
No sex predilection for measles is known.
Age
- Of the 66 cases of measles reported in the United States in 2005, 7 (10.6%) involved infants, 4 (6.1%) involved children aged 1-4 years, 33 (50%) involved persons aged 5-19 years, 7 (10.6%) involved adults aged 20-34 years, and 15 (22.7%) involved adults older than 35 years.1
- Measles in heavily populated, underdeveloped countries is most common in children younger than 2 years.
Clinical
History
- Approximately 10 days after the initial exposure to the measles virus, the classic viral prodrome occurs.
- Fever
- Nonproductive cough
- Coryza
- Conjunctivitis
- Additional prodromal symptoms may include malaise, myalgias, photophobia, and periorbital edema.
- Within 2-3 days, the pathognomonic Koplik spots typically arise on the buccal, gingival, and labial mucosae.
- A rash is present.
- It typically begins at the hairline and spreads caudally over the next 3 days as the prodromal symptoms resolve.
- The rash lasts 4-6 days and then fades from the head downward.
- Desquamation may be present but is generally not severe.
- Complete recovery from the illness generally occurs within 7-10 days from the onset of the rash.
- Modified measles occurs in children who have received serum immunoglobulin after their exposure to measles. The measles symptom complex may still occur, but the incubation period is as long as 21 days, with the same symptoms as measles but milder.
- Atypical measles occurs in individuals who were previously immunized with the killed measles vaccine between 1963 and 1967 and who have incomplete immunity.
- When they are exposed to the measles virus, a mild or nonexistent prodrome of fever, headache, abdominal pain, and myalgias precedes a rash that begins on the hands and feet and spreads centrally.
- The rash is most prominent in the body creases and may be macular, hemorrhagic vesicles, petechial, or urticarial.
- Complications may include pneumonia, pleural effusion, hilar lymphadenopathy, hepatosplenomegaly, hyperesthesia, or paresthesia.
- All persons vaccinated after 1967 received the live attenuated measles vaccine, which is not associated with atypical measles.
Physical
- Patients with measles tend to appear moderately ill and uncomfortable because of their viral prodromal symptoms.
- The Koplik spots are 1-2 mm, blue-gray macules on an erythematous base.
- The measles rash is a maculopapular erythematous rash that involves the palms and soles.
- Lesion density is greatest above the shoulders, where macular lesions may coalesce.
Causes
The cause of measles is a single-stranded RNA paramyxovirus.
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References
MMWR. Morbidity & Mortality Weekly Report. Centers for Disease Control and Prevention. Measles--United States, 2005. MMWR Morb Mortal Wkly Rep. Dec 22 2006;55(50):1348-51. [Medline]. [Full Text].
Centers for Disease Control and Prevention. Update: measles--United States, January-July 2008. MMWR Morb Mortal Wkly Rep. Aug 22 2008;57(33):893-6. [Medline]. [Full Text].
Immunization Schedules. Updated August 11, 2009. Centers for Disease Control and Prevention (CDC). Available at http://www.cdc.gov/vaccines/recs/schedules/default.htm. Accessed November 3, 2009.
Committee on Infectious Diseases, American Academy of Pediatrics. Measles. In: Pickering LK, ed. Red Book: Report of the Committee on Infectious Disease. 27. Elk Grove, Il: American Academy of Pediatrics; 2006:441-452.
Anonymous. Cutaneous viral diseases. Sci Am Med. 1989: 1-2.
Cherry JD. Measles virus. In: Textbook of Pediatric Infectious Diseases. 5th ed. 2004:2283-99.
Mercurio MG, Elewski BE. Cutaneous manifestations of systemic viral, bacterial, and fungal infections and protozoal disease. In: Dermatologic Signs of Internal Disease. 2nd ed. 1995:253-4.
MMWR. Morbidity and Mortality Weekly Report. Centers for Disease Control and Prevention. Measles--United States, 1996, and the interruption of indigenous transmission. MMWR Morb Mortal Wkly Rep. Mar 21 1997;46(11):242-6. [Medline]. [Full Text].
MMWR. Morbidity and Mortality Weekly Report. Centers for Disease Control and Prevention. Status report on the Childhood Immunization Initiative: reported cases of selected vaccine-preventable diseases--United States, 1996. MMWR Morb Mortal Wkly Rep. Jul 25 1997;46(29):665-71. [Medline]. [Full Text].
Moss WJ, Ota MO, Griffin DE. Measles: immune suppression and immune responses. Int J Biochem Cell Biol. Aug 2004;36(8):1380-5. [Medline].
Perry RT, Halsey NA. The clinical significance of measles: a review. J Infect Dis. May 1 2004;189 Suppl 1:S4-16. [Medline].
Semba RD, Bloem MW. Measles blindness. Surv Ophthalmol. Mar-Apr 2004;49(2):243-55. [Medline].
Further Reading
Keywords
measles, rubeola, croup, encephalitis, pneumonia, paramyxovirus, measles virus, encephalomyelitis, MMR vaccine, viral infection, childhood illness, otitis media, thrombocytopenia with purpura and bleeding, myocarditis, hepatitis, pericarditis, severe keratitis
Overview: Pediatrics, Measles