An Overview of the Measles Virus
Measles virus is the
cause of measles. This virus is a single-stranded RNA virus, from the family
Paramyxovirus, of the genus
Morbillivirus. It is closely related to the
rinderpest and
canine distemper viruses.
The measles virus only infects humans. Measles virus is rapidly inactivated by heat, light, acidic pH, ether, and trypsin (an enzyme). It has a short survival time (under 2 hours) in the air, or on objects and surfaces.
References to measles can be found as far back as the 7th century A.D. In fact, the disease was described by Rhazes (Persian philosopher and physician), in the 10th century A.D., as "more dreaded than
smallpox." But all that changed in 1963, when the measles vaccine was first licensed in the U.S.
Prior to 1963, almost everyone got infected with the measles virus; it was an expected life event. Each year in the United States, there were approximately 3 to 4 million cases, and an average of 450 deaths. Epidemic cycles occured every 2 to 3 years. More than half the population had measles by the time they were 6 years old, and 90 percent had the disease by the time they were 15 years old. This indicates that many more measles virus infections were occurring than were being reported; however, after the measles vaccine became available, the number of measles virus infections dropped by 99 percent, and the epidemic cycles diminished drastically.
We still see measles among visitors to the United States and among U.S. travelers returning from other countries. The virus brought into this country sometimes causes outbreaks; however, because most people in the United States have been vaccinated, these outbreaks are usually small. Measles is still a very common illness worldwide.
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