Over the years, many of my Burness colleagues have worked extensively with global health organizations to promote awareness of malaria research and prevention efforts. We take malaria seriously here.

But until this week, I regarded malaria as a tropical or sub-Saharan disease—something that just doesn’t happen here in the United States. After all, the US eradicated malaria during the 1950s.

Except that, between 2000 and 2014, some 22,000 people were hospitalized in the US for malaria, at a cost of about $500 million.

That’s according to a study that just came out in the American Journal of Tropical Medicine and Hygiene, published by our partner the American Society of Tropical Medicine and Hygiene, the world’s leading association of infectious disease scientists and clinicians.

It seems that more and more Americans are traveling to places where malaria is common, but they are not using preventive measures, such as anti-malaria medications and mosquito repellents, even though they are very effective. These travelers become infected, bring the disease back home with them, and get sick. (Men, it seems, are less likely to take preventive measures; 60 percent of Americans infected with malaria are men.)

Not only that, but they create the potential for a resurgence of malaria in the US, if mosquitoes here bite people who are infected and become carriers. According to the Centers for Disease Control and Prevention, the U.S. had 63 local malaria outbreaks between 1957 and 2015.

No other travel-related illness comes close to having the impact that malaria has had in this country.

World Malaria Day is a good time to acknowledge the terrible toll that malaria continues to take in other parts of the world, sickening millions of people and killing hundreds of thousands a year.

But it’s also a good time to remember that we live in an interconnected world. Americans still get sick from malaria, and a couple hundred have even died from it.

So, yes, we should educate and prepare ourselves appropriately before traveling overseas. But we also ought to think more broadly about health and disease and how they happen. Our actions and behaviors affect not only our own health, but also, potentially, the health of others whose lives we’re not even aware we’re touching.

For more, check out this story from the New York Times.