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It’s official. In 2019, the United States (U.S.) is experiencing the nation’s largest outbreak of measles since 1994.
As the pairing of “measles” and “outbreak” screams across the headlines of countless news outlets, the majority of us experience an internal and instinctive shrinking back. But why? Is this learned response necessary, or is it simply the result of scare tactics and media hype?
At an initial glance, measles doesn’t seem so scary. Before the development of a measles vaccine in the 1960s, enduring this disease was essentially a right of childhood passage as most children were infected with the virus by age 15. On an annual basis, an estimated 3-4 million Americans were infected with measles virus and the resulting disease carried a seemingly low death toll. So why has the government required U.S. healthcare professionals and laboratories to report all diagnosed cases since 1912?
The short answer: measles virus is incredibly contagious and can produce harmful, even deadly, complications.
Meet the Contagion
Measles is a human respiratory system infection caused by the measles virus, also known as rubeola. The disease is initially characterized by flu-like symptoms such as high fever, cough, and runny nose. Approximately 3-5 days after symptoms begin, a rash breaks out, often accompanied by a fever spike that reaches over 104˚F. Tiny red spots and bumps cluster on the infected person’s face, spreading to the arms, trunk, thighs, lower legs, and feet.
By the time these symptoms appear, though, the measles virus has already been busy at work inside the infected person’s body for up to 2 weeks.
The course of a measles virus infection is characterized by two periods: an incubation period and a contagious period. The incubation period begins with infection. When measles virus enters a person’s airway, it is gobbled up by immune cells, which shuttle the virus to nearby lymph nodes. Upon arrival, the measles virus aggressively reproduces. The virus potently suppresses a person’s innate immune response, enabling itself to replicate unchecked, spreading to more organs and ultimately causing a systemic infection. Cue the fever and runny nose.
At this point, or possibly even days before, the contagious period has begun. Inside the body, measles virus has hitched a ride with more immune cells, returning to the upper airway, particularly the trachea. Once again, the virus aggressively reproduces, creating a high load of measles in the person’s windpipe. During this time, a person still may not even realize they have measles. Symptoms are only just emerging and frankly, a fever, runny nose, and cough isn’t a dead giveaway for measles.
But then, the rash breaks out.
The appearance of the rash is notable for several reasons. First, the measles-ridden individual is likely feeling their worst, with their fever spiked, several days of early symptoms, and the rash overtaking their body. Second, it evidences the arrival of the cavalry; the person’s immune system is fighting back and the contagion will soon be cleared from the body. Finally, the rash provides a window of transmissibility, or, in other words, the time frame in which an infected person can spread measles to other susceptible individuals. A person infected with measles is thought to be contagious for 8 days total – the 4 days before and after the appearance of the rash.
According to the Centers for Disease Control and Prevention (CDC), measles virus is so contagious that one infected person will pass the virus to approximately 90% of the susceptible people close to them,5 which typically averages out to 12-18 other people. In contrast, one person infected with influenza, which is also a respiratory system infection, will, on average only, spread the illness to 1-4 others.
Remember how measles aggressively replicates in the trachea during the contagious period? A high viral load in the last few inches of an infected person’s respiratory tract is the ideal location for the virus to be aerosolized. The infected person coughs and sneezes, and without realizing it, spews large amounts of measles virus into the air. Traveling on aerosolized droplets of spit or snot, measles floats through the airspace, some of it landing on nearby surfaces, waiting to meet a new host.
Measles virus can live for up to two hours in contaminated airspace or on surfaces. When others come into contact with the virus – whether through the airspace, or by touching a contaminated surface and subsequently touching their eyes, nose, or mouth – they’re at risk for infection. Unless, of course, they’ve been vaccinated, which dramatically reduces their risk.
After a successful vaccination program initiated in 1989, measles was declared eliminated from the U.S. in the year 2000. “Elimination,” in this case, means that measles hasn’t been transmitted continuously for more than a year. Essentially, elimination occurred because there weren’t enough susceptible people in the U.S. for measles to infect and subsequently jump from person to person. However, measles is far from eliminated in other parts of the world, such as developing countries, where it’s endemic, or extremely common. As a result, over the past 20 years, most measles cases have been brought to the U.S. by international travelers. But measles cases are on the rise in developed countries including the U.S, putting the unvaccinated at risk.
A measles outbreak occurs when there are three or more confirmed cases in a month. Currently, the U.S. is experiencing the largest outbreak of measles since elimination, with cases reported in 23 states.1 Once an outbreak has occurred, local, regional, and national health departments, laboratories, and hospitals take steps to control the spread of measles. For example, infected persons are isolated while they’re contagious and susceptible individuals get vaccinated.
…and Its Potential
But really, who cares if measles tears through the country like wildfire? It’s not that dangerous, right?
Although many individuals infected by measles virus will recover, others will experience complications, and others still will die. Sadly, the population hardest hit by measles is unvaccinated young children. In 2017 alone, 110,000 people died from measles virus infections worldwide, most of them children under 5 years of age.
Common complications of measles include ear infections and diarrhea. Unpleasant, yes, but not deadly. However, measles virus infection sometimes leads to severe complications, particularly in children under the age of 5 and adults over the age of 20. Approximately 1 out of every 20 children with the measles gets pneumonia and 1 in 1,000 develops encephalitis (swelling of the brain), both of which may require hospitalization and can result in long-term, or even permanent, damage. Even with the best medical care, 1-2 out of every 1,000 children with the measles will die. Another at-risk population is pregnant women. Measles virus infection during pregnancy can lead to premature birth or a low-birth-weight baby.
The Best Way to Prevent Infection
The best chance to prevent measles infection is vaccination. If you were born before 1957, chances are you’ve had measles before and that you have natural immunity. If you were born between 1963 and 1968, you probably received the first version of the measles vaccine, one that contained a dead version of the virus. In 1968, the vaccine was redeveloped as one that contained a live, but weakened, version of the virus, and since then, it has been the only measles vaccine used in the U.S. One dose is 93% effective at preventing measles. A second dose bumps that percentage up to 97%.
Typically, the measles vaccine is given in combination with mumps and rubella (MMR) or mumps, rubella, and varicella zoster (chickenpox) (MMRV). Years ago, the MMR vaccine gained public notoriety due to the promotion of an unethical, wrong, and ultimately retracted, 1998 study that continues to unfairly haunt perceptions of a safe and effective vaccine.11 Repeatedly, the scientific community has studied the question raised from that report: One analysis examined over one million children and found no association between autism and the MMR vaccine.
The CDC recommends that all children receive two doses of the MMR vaccine starting at 12-15 months of age and that all teens and adults make sure they’re up to date on their MMR vaccination. Especially if you’re traveling, it’s a good time to check your vaccination status. Ultimately, consider the following: due to herd immunity, staying up to date on your measles vaccination will not only save yourself the hassle of a nasty infection. You’ll also be protecting those who cannot be vaccinated and those who belong to at-risk groups, such as children under the age of 5, from a contagion that will secretly reproduce in their little bodies and can cause permanent harm and even death.
Laura Ruhge, PhD, is a scientific writer in Chicago, IL. She earned her Ph.D. in Life Sciences from Northwestern University, where she studied the molecular mechanisms of herpes virus infection.