PARIS — Ebola. Toxic air pollution. The HIV epidemic. Given the plethora of health problems we face, all-but-eradicated diseases like measles, polio and smallpox should be the least of our concerns.

And yet, due to what the World Health Organization (WHO) calls "vaccine hesitancy" — the reluctance or refusal to vaccinate despite the availability of vaccines — those bygone illnesses are making a comeback. And it's a serious problem, so much so that WHO opted to include vaccine hesitancy in its latest "top 10" list of global health threats.

Being hesitant towards vaccinations does not necessarily mean being opposed to inoculations. But it does leave a metaphorical window open for people to be sucked into the so-called "anti-vaxx" movement. Most prevalent in the United States, the anti-vaxx movement is widely recognized as a grouping of individuals who are concerned about the institution of vaccinations. Often, they distrust the healthcare system in general.

Anti-vaxxers choose not only to opt out of vaccinations, but also promote their position as superior to the status quo. And with the help of social media platforms like Facebook and YouTube, the controversial movement has been able to cross both cultural boundaries and physical borders with its message of misinformation and conspiracy theories. From the United States, it has thus spread far and wide — to Brazil, the Philippines and beyond.

United States

All 50 U.S. states require children to be vaccinated to enter schooling and day-care, but 18 states allow exemptions on the basis of philosophical beliefs, according to the National Conference of State Legislatures (NCSL). These views can range from personal, moral or other beliefs that conflict with receiving inoculations. And in places where people have used these exemptions to opt out — in pocket communities in the Pacific Northwest, for example — measles is making a comeback.

Anti-vaxxers choose not only to opt out of vaccinations, but also promote their position as superior to the status quo.

Since the start of the year, Washington State's Clark County Public Health has had 50 reported cases of the measles virus. Of those, 35 cases involved children 10 and under, and 43 of the 50 people infected were unvaccinated. Health authorities are looking at more than 10 other possible measles cases in the area as the outbreak continues.

Philippines

An anti-vaxx movement of sorts also took root in the Philippines in recent years, sparked by concern over a vaccine for dengue fever. The producer, Sanofi Pasteur, acknowledged that its dengue vaccine is not as effective as advertised and has, in some cases, caused severe infections in people who had not previously been exposed to the disease.

Health worker preparing vaccinations in the Philippines — Photo: Herman Lumanog/ Pacific Press/ ZUMA

This data, coupled with fear-mongering by political leaders, prompted many people to question (and avoid) vaccinations in general, according to Philstar. The result, again, has been a resurgence of measles. In just the first six weeks of 2019, the Philippines already had more than 4,000 cases of measles and at least 70 confirmed deaths.

Israel

The disease has also reappeared in Israel, which in 2018 had its first death from measles in 15 years. The victim was an unvaccinated child belonging to an ultra-orthodox Jewish community in Jerusalem, according to Israeli newsource, The Times of Israel. Many members of insulated communities within Israel refuse to vaccinate their children on the belief that, due to their limited contact with mainstream society, they are protected from infections that would otherwise harm them. The facts suggest otherwise: In the past year alone, there have been more than 800 measles infections in Israel. Of those, more than 200 were linked to an ultra-orthodox community in Safed that refuses to vaccinate.

Italy

When Europe faced its own measles outbreak in 2017, Italy was particularly hard-hit. The Mediterranean nation accounted for 34% of all cases. Last year, Italy no longer required students to provide proof of vaccination upon entry to public schooling, after a new law pushed through by the majority party in the Italian Parliament, the Five Star Movement (M5S), which includes anti-vaxx representatives. As a result, only about 85% of Italy's pediatric population is now vaccinated against measles, well below the 95% needed to keep the virus from spreading and becoming dangerous for the overall population.

Yet just this week, in light of the growing risk of measles spreading further, Italy reversed itself and required kids to be vaccinated to enter schools. In a recent commentary in Milan-based Corriere della Sera, three Italian researchers explored the anti-vaxx phenomenon in relation to internet activity. "Getting informed about the controversy around the safety and effectiveness of vaccines can be complicated because in reality no controversy exists," wrote the trio, who have authored a study in the "Journal of Experimental Psychology: Applied. "However the presence of different perspectives (scientific and otherwise) pushes internet users in the trap of "errata par condicio" (errors by equal time)."

Anti-vaxx protestors demonstrate in Rome — Photo: Patrizia Cortellessa / Pacific Press/ ZUMA

Brazil

A particularly deadly outbreak of Yellow Fever suggests that anti-vaxx ideas are marking inroads in Brazil as well. In 2018, WHO confirmed some 700 cases of the mosquito-borne illness. Of those, approximately 200 were fatal, a huge portion when considering that when people are vaccinated, the mortality rate associated with Yellow Fever infection ranges from 3% to 7%.

The presumption, then, is that people have been opting against the vaccine, perhaps in response to social-media misinformation linked to a previous Yellow Fever outbreak in 2016. That outbreak prompted masses of people to vaccinate. But when large populations are all vaccinated at once, the rare side effects are bound to occur more frequently due to the sheer numbers showing up. Anti-vaxxers used those exceptions to spread false ideas about the vaccine, Brazilian news source GloboNews reported. That, in turn, resulted in fewer people being vaccinated. And when the next big outbreak came, sadly, a greater number of people died.