Measles, an RNA virus, has caused illness and death worldwide for centuries. It was first referenced in the medical literature in Persia, during the ninth century. In 1757, a Scottish physician named Frances Home discovered that measles was caused by a pathogen which could be identified in blood.1
In the U.S. during the early 1900s, thousands of people, mostly children, were sickened and died annually from measles. By 1912, laboratories were required to report all diagnosed cases when it became a nationally notifiable disease. At that time, 6,000 measles-related deaths were reported annually in this country.2
Progress in the fight against measles took a powerful turn in 1963, with the advent of the first distributed measles vaccine. School vaccination requirements all but eradicated the disease during the 1990s.3
Measles was officially declared eliminated in the U.S. in 2000. Yet today, measles outbreaks have reemerged. With them comes the need for increased knowledge and familiarity with collection protocols, specimen handling, and disease confirmation in the laboratory. As is often the case, pathologists and laboratory professionals are on the front lines of fighting and controlling a deadly disease.
To find out why measles has reemerged with a vengeance and what this means for laboratory professionals and pathologists, we turned to pathologist Mary K. Klassen-Fischer, MD. Dr. Klassen-Fischer is the lead author of “The Reemergence of Measles: What Every Pathologist Needs to Know,” which appears in the January 2023 edition of the American Journal of Clinical Pathology.4 (The information provided by Dr. Klassen-Fischer in this article represents her opinions, and not necessarily those of the Department of Defense).
The threat of measles was eliminated in the U.S. more than two decades ago. What altered that course, bringing it back into an area of concern? According to Dr. Klassen-Fischer, multiple factors were and continue to be at play, both at home and overseas. “The reemergence of measles is primarily the result of decreased vaccination rates, caused by vaccine hesitancy,” she explains. “Vaccine hesitancy has resulted from misinformation, and decreased confidence in science. Measles vaccine access has also decreased because of many factors. The coronavirus pandemic, immigration, dysfunctional health care systems, poverty, refugee crises, political instability, and climate change have all had an effect.”
COVID-19 didn’t start the measles fire, but it did throw accelerant on it. According to UNICEF, mass measles immunization campaigns were halted in more than 25 countries in 2020, when COVID-19 hit in earnest. But even before that severe disruption took place, children worldwide were at risk. Before COVID, more than 13 million children worldwide remained unvaccinated and vulnerable.5 Measles may have been eliminated in the U.S., but it never ceased to ravage other countries.
Currently, widespread measles outbreaks are occurring throughout the world in countries such as India, Yemen, and Somalia.6 As we know, pathogens can reach the U.S. from anywhere. But the threat of measles isn’t only generated from abroad.
Measles, once thought of as an inevitable childhood rite of passage, is incredibly contagious. According to the Centers for Disease Control and Prevention (CDC), nine out of 10 unprotected people who are exposed to measles will catch it. However, misperceptions about the potential severity of measles may be playing a role in vaccine hesitancy, and the spread of measles, in the U.S. today.
Many of today’s parents and grandparents grew up surrounded by measles. During the 1950s and early 1960s, most children got measles by age 15. Of the 3 to 4 million people infected annually, 400 to 500 died and 1,000 had serious complications, such as encephalitis. But most kids simply missed a week of school.
These experiences have generated a dangerous assumption, fueled by pseudo-scientists and the spread of attention-grabbing misinformation, that measles isn’t dangerous. Of course, that was never the case. “There has always been a risk for serious complications from measles, including death,” says Dr. Klassen-Fischer.
She notes that the risk for complications is greater in immunocompromised or malnourished people, and that their numbers are higher today than in years past. “More people in developed countries are now immunosuppressed, due to medical treatments for malignancy and autoimmune disease, than there were in the pre-Measles-vaccine era. We’re also seeing significant malnutrition worldwide, due to the same conditions that have led to decreased vaccination,” she adds.
Measles can be mistaken for any illness that causes a rash combined with respiratory symptoms. Measles can also present without a rash. Laboratory confirmation of suspected measles cases is an essential component of predicting, and stemming, outbreaks. According to the CDC, the detection of measles-specific IgM antibodies in serum, and real-time RT-PCR of measles RNA in respiratory specimens, are the most commonly used methods of confirmation. Urine samples may also be used to detect the virus.7
Dr. Klassen-Fischer feels that familiarity with the histopathologic findings of measles will enable pathologists to make an early diagnosis in unsuspected cases, as well as being able to confirm disease in suspected cases. This could have a staggering impact on the reduction of community transmission.
“Diagnostic viral cytopathic changes may be observed in a child’s appendectomy or tonsillectomy specimen before the appearance of a rash, Koplik spots, or conjunctivitis, allowing earlier isolation to prevent infection among contacts. Also, characteristic histopathologic features may be identified in specimens from immunosuppressed individuals who did not mount an adequate antibody response and, therefore, did not develop a rash,” she explains.
Dr. Klassen-Fischer stresses the need for training in the lab, so that pathologists and laboratory professionals can recognize and report histopathologic findings in measles. Dr. Klassen-Fischer’s article from the Joint Pathology Center, published in AJCP, provides everything pathologists need to know about recognizing this disease. The article has many photomicrographs of various tissues, especially in the supplemental figures available online. “We are fortunate at the Joint Pathology Center to have a large historical collection of specimens dating back to 1862,” she says.
Clearly, the role of pathologists and laboratory professionals in protecting public health is substantial. Diagnosing measles in the lab, and acting promptly when it is found, are essential elements to the cessation of disease progression.
“Laboratories can help ensure that measles cases get reported promptly to public health departments. We can all help to prevent measles by getting our children (and ourselves, if appropriate) vaccinated, by sharing information, and by not spreading disinformation,” adds Dr. Klassen-Fischer.
Many of today’s medical professionals, both in and out of the lab, entered the field after measles was thought to be long gone. Educating pathologists about the histopathologic features of measles is an imperative step towards saving lives and eliminating measles, finally and permanently.
Measles history. (2020). https://www.cdc.gov/measles/about/history.html
Haelle, T. Why it took so long to eliminate measles. (2019). https://www.history.com/news/measles-vaccine-disease
Klassen-Fischer, M.K., et al. The reemergence of measles: what every pathologist needs to know. (2022). https://academic.oup.com/ajcp/article/159/1/81/6782944?searchresult=1
Over 13 million children did not receive any vaccines at all even before COVID-19 disrupted global immunization – UNICEF. (2020). https://www.unicef.org/press-releases/over-13-million-children-did-not-receive-any-vaccines-all-even-covid-19-disrupted
Global measles outbreaks. (2023). https://www.cdc.gov/globalhealth/measles/data/global-measles-outbreaks.html
Measles (rubeola) clinical features. (2020). https://www.cdc.gov/measles/hcp/index.html#:~:text=Diagnosis%20and%20laboratory%20testing,-Healthcare%20providers%20should&text=Detection%20of%20measles%2Dspecific%20IgM,methods%20for%20confirming%20measles%20infection