It is not a pretty sight – a newly born child with an unusually small head and brain damage. The working theory is that these abnormalities are caused by a virus, known as the Zika Virus, delivered by a certain strain of mosquito. It is believed that millions of people in the Americas, particularly South America, are infected, but that for the most part, “the infection causes no symptoms and leads to no lasting harm.” (See the New York Times article “Short Answers to Hard Questions About Zika Virus.)

And as the New York Times emphasized in another article, the connection between Zika and abnormalities in newborns is still unproven: “…the big question is whether Zika is responsible for the huge increase in birth defects reported by doctors, hospitals and other medical officials in Brazil over the last few months. That connection has still not been proved.”

And yet, it is the fear Zika creates that is of most concern to people in the Americas, particularly in Brazil, where the Olympic and Paralympic Games will be held in August and September this year. Millions of people from all over the world will visit, and while transmission of the Zika virus is unclear, the fear of the spread of the disease has increased. Will people who get bit in Rio de Janeiro become infected, and can they spread the virus in their own country via mosquitos locally? Will pregnant women be at significant risk?

In fact, The Center for Disease Control in the United States has issued a warning against travel for pregnant women and women trying to become pregnant to over 20 countries, primarily in the Caribbean, Central and South America, including Brazil. And the World Health Organization has declared Zika an “international health emergency.”

In the run-up to the London Olympics in 2012, there were fears of a flu pandemic. The Chinese government publicized the fact that thousands of additional hospital beds would be kept open in case of an outbreak of SARS. Fortunately, those particular fears never became an issue, and ultimately, those epidemics never emerged. Will Zika be different? One concern is the unknown nature of the Zika virus. The American Psychological Association explained the impact of the fear of the unknown disease in this article.

Research has shown that different threats push different psychological buttons. Novel, exotic threats like Ebola or avian flu raise anxiety levels higher than more familiar threats do. This reaction may have to do with our amygdala, which research suggests plays a role in detecting novelty as well as processing fear. In one recent study, for example, Nicholas Balderston and colleagues at the University of Wisconsin–Milwaukee found that activity in the amygdala increased when participants looked at unfamiliar flowers right after seeing pictures of snakes (PLOS ONE, 2013).

And, at the same time, people often under-react to familiar threats. For example, influenza sickens as much as 20 percent of the population a year, and kills thousands. Yet because most people have had the flu and survived, or know someone who has, people may feel less urgency toward getting a seasonal flu vaccine. This may help explain why the U.S. vaccination rate for the 2013–14 flu season was only 46.2 percent.

I feel for the organizers of the Rio Olympics. As I had described in a previous post, one