In certain pockets of America, measles diagnoses have been spreading at previously unprecented rates.

In 2017 there were 58 confirmed cases of the illness in Minnesota – the largest outbreak the state had seen in 30 years. Similarly, in 2008, a large outbreak occurred in California, which was thought to originate from a seven-year-old boy, who had not been vaccinated.

Less than a decade earlier, measles had been largely eliminated in the US. The gradual resurgence can, researchers say, be directly attributed to people who were not vaccinated.

Before measles vaccinations were introduced in 1963, the illness could be deadly. In the 1960s, there were several million cases, thousands of hospitalisations and 500 deaths per year. Meanwhile in Australia, a 2016 report concluded that 23 deaths from a host of diseases could have been prevented by vaccination between 2005 and 2014. And what’s more, such vaccinations were readily available.

Those that do not vaccinate often choose not to. They are called “anti-vaxxers” and they largely believe that vaccinations are harmful – and, often, that pharmaceutical companies (and others) cover up damaging effects of vaccinations. It is but one of many conspiracy theories that flies in the face of scientific evidence – a quick internet search throws up hundreds.

Similarly, climate change deniers are convinced that the Earth is not warming, and some say that scientists are tweaking evidence to make it appear so. Those that believe in one conspiracy, are in turn more susceptible to believing others.

While some conspiracy theories are relatively harmless – the argument that Nasa faked the Moon landing, or bizarrely, that Beatle Sir Paul McCartney died long ago with a doppelganger taking his place ever since – others have damaging ripple-effects.

With new insights, researchers are getting closer to understanding more of the factors involved. This will, they hope, help mitigate some of the very real dangers and societal divides that conspiracy theories encourage.