Children’s health has been getting better and better in the U.S. for more than a century. That’s due in no small part to vaccines that protect children — and adults — from diseases that could otherwise be fatal.

Vaccines have, over and over again, led to near elimination of some of the worst diseases humans have faced. Smallpox has been completely eradicated from the face of the planet thanks to a vaccine. Polio and malaria are soon to disappear, as well. The U.S. can also thank vaccines for the elimination of yellow fever, diphtheria and measles.

Except — measles is now staging a comeback, thanks to a different kind of disease: a viral strain of conspiracy-theory-laced lies.

While not a medical disease, these lies seem to infect individuals and spread through communities in much the same way a disease might.

Let’s call this different kind of disease “conspiracitis.”

There have been 159 confirmed cases of measles in 10 states in 2019, including one child from Kentucky who was diagnosed with the disease last month. These outbreaks are made possible by conspiracitis, which is spread largely over the internet. It eats away at the logical parts of people’s minds, making them believe they would be better off not protecting themselves from disease because of disproved, completely fabricated fears.

When someone suffering from conspiracitis contracts a disease such as measles outside the U.S., they can bring it back into the country. Then, it can spread to their friends and family if they have also chosen not to protect themselves.

These clusters of unprotected people are not only putting themselves at risk; they are reducing what’s known as “herd immunity” — the ability to protect all of a population by vaccinating a high percentage.

Without herd immunity, we cannot protect those who are too young to be vaccinated or have legitimate health problems that prevent vaccination. It is these most vulnerable members of our communities who parents put at risk against their will.

There is work being done to counteract the spread of conspiricitis.

Some websites such as Pinterest, Facebook and YouTube have created new policies that limit the spread — and in some cases profitability — of anti-vaccine posts and videos, according to Vox.

Government officials are looking into how to promote the spread of useful information, as well. Brett Guthrie, a U.S. representative from Kentucky, helped lead a congressional hearing on the recent measles outbreaks Wednesday.

During his opening remarks, Guthrie noted that back in 2000, “measles was declared eliminated in the United States … because the nation had gone more than 12 months without any continuous disease transmission. Public health experts believe the U.S. achieved this progress because of a safe combination of measles, mumps rubella — or MMR — vaccine, high vaccination rates and a strong public health system to detect and respond to outbreaks.”

But from 2011 to 2017, the average number of measles cases reported annually was 217.

“These outbreaks are tragic since they are completely avoidable,” Guthrie said.

Dr. Anthony Fauci, the director of the National Institute of Allergies and Infectious Diseases at the National Institutes of Health, warned during the hearing about the problem of misinformation.

Fauci testified, “the spread of misinformation that leads people to make poor choices, despite their well-meaning, is a major contributor to the problem we’re discussing.”

Conspiracitis poses a threat to the progress we’ve made in health for decades. It’s a dangerous problem that can be highly contagious, but fortunately, there is a vaccine: the facts.