Measles is highly contagious infectious airborne disease caused by the Measles morbillivirus (MeV), a single-stranded enveloped RNA virus. Humans are the only known natural host of the Measles Virus, and there are no animal reservoirs are known to exist.
Other names for measles include morbilli, rubeola, red measles, and English measles. However, despite the names, both rubella, also known as German measles, and roseola are different diseases caused by unrelated viruses.
Measles symptoms appear 7 to 14 days after contact with the virus.
The classic measles rash appears 3 to 5 days after the first symptoms (so typically 2 to 3 weeks after exposure). It usually begins as flat red spots that appear on the face at the hairline. They then spread downward to the neck, trunk, arms, legs, and feet.
Measles is highly contagious. If one person has it, up to 9 out of 10 (90%) people nearby will become infected if they are not protected (by vaccination or prior infection).
An infected person can spread measles to others even before knowing they have the disease. You can spread measles to others from 4 days before through 4 days after the rash appears.
It spreads through the air when an infected person coughs or sneezes. You can get measles just by being in a room where a person with measles has been. This can happen even up to 2 hours after that person has left.
If other people breathe the contaminated air or touch the infected surface, then touch their eyes, noses, or mouths, they can become infected.
Measles is a highly contagious virus that lives in the nose and throat mucus of an infected person. It can spread to others through coughing and sneezing.
Measles is a highly contagious acute respiratory infection that is spread through air when an infected person sneezes or coughs, as well as through direct contact with mouth and nasal secretions of an infected person. Measles infections typically resolve after about three weeks.
Symptoms usually develop 10-12 days after exposure, beginning with fevers (often as high as 105°F) along with cough, runny nose, and eye redness. The fever generally lasts approximately a week after symptoms begin. The characteristic "Measles rash" typically starts to appear two to four days after the initial symptoms.
A specific type of rash, called Koplik's spots, sometimes forms two to three days after symptoms. These small white spots commonly seen on the inside of the cheeks, opposite to the molars. They are described as looking like "grains of sand" on a red background. These spots appear early in infection, before the person reaches peak infectiousness, so if they are spotted quickly and the person is isolated, it can drastically limit the spread of disease. It is important to know that these Koplik's spots are also considered diagnostic for measles.
The classic "measles rash" is a flat red area of the skin covered with tiny raised red bumps (maculopapular rash). It typically does not appear until three to five days after the initial symptoms. It usually starts on the back of the ears before spreading to the head and neck. It eventually spreads throughout the entire body and is often itchy. The rash can last up to eight days, beginning as a red rash and then changing to dark brown before disappearing.
There are no specific antiviral treatments for measles, but supportive care can improve outcomes.
Measles causes acute immuno-suppression, even in healthy individuals, which can lead to a variety of complications, either during or shortly after infection.
Some people may suffer from severe complications, such as pneumonia (infection of the lungs) and encephalitis (swelling of the brain). They may need to be hospitalized and could die.
Subacute sclerosing panencephalitis (SSPE) is a very rare, but fatal disease of the central nervous system that results from a measles virus infection acquired earlier in life.
The origin of measles is thought to have been zoonotic, evolving from Rinderpest (an infectious viral disease found in cattle, bison, and other hooved animals). A precursor to measles began sporadically infecting humans as early as the 4th Century BC, and over time evolved to become a distinct virus that infected humans.
Sometime between AD 1100 and 1200, the measles virus fully diverged from rinderpest, becoming a distinct virus that infects humans. It was at the time that medieval European cities had grown to a size to sustain an epidemic (population >500,000).
In the Middle Ages, measles was referred to by the Latin word morbilli (''little disease'', derived from morbus). In the 11th-12th centuries, several measles epidemics were reported in Europe. It is generally accepted that the disease was widespread in Europe and in South and East Asia, India and China during the Middle Ages.
The first clinical description of measles, and its distinction from smallpox and chickenpox, is credited to the Persian physician Muhammad ibn Zakariya al-Razi (also known as Rhazes), who published The Book of Smallpox and Measles in the 9th century.
According to him, smallpox is a transitional state from childhood to adulthood during which the blood ferments like wine, which explains why almost all children contract the disease. Measles is a different disease caused by too much bilious blood. He admits that even an experienced physician may have difficulty distinguishing smallpox from measles. Both diseases are eruptive fevers but, unlike measles, smallpox is much more severe with high mortality and leaving indelible skin scars on survivors. The measles rash does not cause ulceration and disappears by peeling.
In the 11th century, Avicenna clarified these differences by also distinguishing "attenuated measles", which was later interpreted as rubella.
During the Renaissance period, with the increase in global trade and exploration, measles spread worldwide. During the 17th century, there were two notable measles epidemics in England and Scotland, in 1670 and 1674. It was from these epidemics that the Englishman Thomas Sydenham wrote the first modern description of the disease in his On the Measles, published in 1693; in this work he also distinguished measles from scarlet fever and smallpox. He also coined the term measles, which came from the medieval English mesles and the Latin misella (diminutive of miser, misery).
In 1757, Scottish doctor Francis Home discovered that measles was caused by a pathogen: he transmitted the disease to healthy individuals using the blood of infected patients and demonstrated that it was caused by an infectious agent.
And in 1846, during an epidemic in the Faroe Islands, the Danish physician Peter Panum meticulously studied and described the epidemiology of the disease, providing the first accurate account of the disease's natural history, including its incubation period and period of infectivity. \
In 1896, the American physician Henry Koplik (1858–1927) described a characteristic indicative of measles, as bluish-white patchy spots on the inside of the cheek that shortly precedes rash onset. These spots are now known as Koplik's Spots.
By the 18th century, measles was endemic throughout Europe, spreading virtually uninterrupted through the early 20th century. Measles is now an endemic disease globally, meaning that it is continually present in the population and resistance is through either vaccination or prior infection. In Measles-naive (not previously exposed to measles) populations, exposure can be devastating.
Measles is estimated to have killed about 200 million people worldwide between the years of 1855 and 2005.
In 1912, measles became a nationally notifiable disease in the United States. In the first decade of reporting, an average of 6,000 measles-related deaths were reported each year.
In the decade before 1963, when a vaccine became available, nearly all children got measles by the time they were 15 years of age.
The viral nature of the disease was first demonstrated in 1911 by John Anderson and Joseph Goldberger, when they successfully infected rhesus monkeys with measles from the blood of infected patients, which resulted in the monkeys developing a discrete rash and fever.
In 1954, during a measles outbreak at a boarding school outside Boston, Massachusetts, Drs. John Enders and Thomas Peebles, from Boston Children's Hospital, collected blood samples from several of the ill students at the boarding school to try and isolate the virus and create a vaccine.
They succeeded in isolating the measles virus from the blood of 13-year-old David Edmonston, identifying the measles virus as a morbillivirus (family Paramyxoviridae), which adapted to human infections from the rinderpest virus around the 6th century BCE.
The isolated virus was adapted and propagated on chick embryo tissue culture, and was known as the "Edmonston-B strain", named after young David Edmonston, whose blood led to its discovery.
John Franklin Enders, Peebles’s boss, often called ‘the father of modern vaccines’, developed the measles vaccine from the ‘Edmonston-B’ strain and used as the basis for most live-attenuated vaccines to this day.
Enders and his team tested their measles vaccine on small groups of children from 1958 to 1960, before beginning trials on thousands of children in New York City and Nigeria. In 1961 it was hailed as 100% effective and the first measles vaccine was licensed for public use in 1963.
In 1968, an improved and even weaker measles vaccine, developed by Maurice Hilleman and colleagues, began to be distributed. This vaccine, called the Edmonston-Enders (formerly "Moraten") strain has been the only measles vaccine used in the United States since 1968.
In 1971 Hilleman combined the recently developed vaccines against measles, mumps and rubella into the MMR vaccine, administered as a single shot, with one booster dose following – and in 2005, the varicella (chickenpox) vaccine was added, to make the combined MMRV vaccine.
The World Health Organization (WHO) defines measles elimination as:
“the absence of endemic measles virus transmission in a defined geographical area (e.g. region or country) for at least 12 months in the presence of a surveillance system that has been verified to be performing well.”
Individual countries introduced mass vaccination programmes against measles at the national level from the 1960s on, and the first internationally focused measles immunization programmes took place in Africa from 1966.
Measles elimination efforts in North and South America started in 1991, and all those 9-15 years of age in the region were vaccinated with an additional dose of measles vaccine. The strategies for elimination in use today were first developed and implemented in the Region of the Americas.
In Europe, the first country to eradicate measles was Finland in 1993, with two-dose vaccination starting in 1982 and a 96% coverage since 1991.
Between 2000 and 2023, measles vaccination prevented more than 60 million deaths worldwide.
In 1978, the CDC set a goal to eliminate measles from the United States by 1982. While this goal was not met, widespread use of measles vaccine drastically reduced the disease rates. By 1981, the number of reported measles cases was 80% less compared with the previous year. However, in 1989, after multiple measles outbreaks among school-aged children, the recommendation of a second dose of the MMR vaccine was added. Following widespread implementation of this recommendation, reported measles cases declined even more.
Measles was declared eliminated from the United States in 2000. This meant the absence of the continuous spread of disease was greater than 12 months. This was thanks to a highly effective vaccination program in the United States, as well as better measles control in the Americas region.
The United States has maintained measles elimination status for over 20 years. If a measles outbreak continues for a year or more, the United States could lose its measles elimination status.
Between Andrew Wakefield's fraudulent study published in The Lancet in 1998 linking autism to the MMR vaccine, and the widespread misinformation pushed by anti-vaccination groups, vaccination rates in high-income countries began to drop below the levels required for herd immunity. Because measles is so contagious, the threshold needed for community protection is also extremely high, requiring at least 95% immunity (either through vaccination or prior infection) among the population to prevent epidemics.
This drop in vaccination rates led to a resurgence of measles cases in England, the U.S. and Canada.
Even though the British General Medical Council ruled that Andrew Wakefield engaged in severe misconduct and was barred from practicing medicine; this and the formal retraction of his study in The Lancet did not happen until 2010. The damage had been done.
In the past decade, with decreasing vaccination rates, the number of measles cases and outbreaks has risen. A global measles outbreak in 2019 led to a substantial global increase in measles cases worldwide compared to 2018, reaching highest number of reported cases in 23 years. According to the joint CDC/WHO publication, Progress Toward Regional Measles Elimination — Worldwide, 2000–2019, measles cases worldwide rose to 869,770 in 2019; the highest number reported since 1996, and included increases in all WHO regions. Global measles deaths climbed nearly 50 percent since 2016, claiming an estimated 207 500 lives in 2019 alone.
