One of the most contagious diseases on Earth is forging a path through the unvaccinated in the United States, reaching its highest infection rate since 1996. The disease is measles, now clocking in at 204 confirmed cases nationally as of this writing. Most people infected, about 86 percent, were not vaccinated. Of the remainder, many were partially vaccinated.
Before the introduction of a vaccination against measles, about 3 to 4 million people each year in the United States would catch the measles, tens of thousands would be hospitalized, and a few hundred would die, according to the Centers for Disease Control and Prevention (CDC). Catching measles is easy to do: the virus can survive for two hours in the air or on surfaces, propelled there by a cough or sneeze from an infected person. It’s also a stealth virus – people are contagious before they show symptoms.
Once you are unwittingly exposed and have snuffed the measles virus up your nose or into your lungs, the virus replicates (makes more viruses) in the sensitive tissues lining the respiratory tract. Then, it moves into your lymphoid tissues, the seat of your immune defenses, and flourishes. After a week or two, you will finally show symptoms. During that interval, though, every cough or sneeze around others translates into exposure for the unvaccinated.
For many people who are infected, the disease means a period of discomfort from the high fever, cough, red eyes, and characteristic bright red rash. But in a few people, the virus will take root in the lungs, causing an often-fatal pneumonia in one of twenty cases. Of the hundreds of thousands of deaths annually worldwide from the measles, which kills about one or two of every 1,000 people infected, virus-related pneumonia underlies the majority. The virus may also make its way to the brain, where it can cause a sometimes-fatal inflammation known as encephalitis in one of 1,000 cases. People who survive the encephalitis may still have long-term chronic effects, including deafness and seizures.
As of this writing, measles cases have popped up this year in Wisconsin, New Mexico, Minnesota, Pennsylvania, Florida, New York, Indiana, Vermont, Utah, Virginia, Washington, Iowa, Texas, and other states. Globally, outbreaks are growing intense (PDF) in some parts of the world. According to the World Health Organization, there have been almost 170,000 suspected measles cases in 2011 to the present (September 22), and those are only the recorded ones. The virus is compounding the famine and homelessness in the Horn of Africa and making its way through Europe, where France has seen a reported 7,500 cases so far this year, according to the CDC. Indeed, the CDC notes that many cases in the United States have been traced to foreign travel.
The preventive, of course, is vaccination. Measles strikes hardest among the unvaccinated or the partially vaccinated. Most at risk are the very young, under age five, or those with compromised immune systems.
Bottom line: Measles cases are at their highest in the United States since 1996, topping 200 and popping up nationwide. The vast majority of those infected are unvaccinated. The recommended preventative is vaccination.
Dr. Emily Willingham came to EarthSky from The Biology Files. Her background includes a PhD in biological sciences, a bachelor's degree in English, and a published book: The Complete Idiot's Guide to College Biology. She is a scientist, writer, editor, teacher, autism & ADHD parent, and "all around opinionator." Says Emily: "Got an English BA & biology PhD, & I'm not afraid to use them, often together."