Scientists suggest that the lethal hantavirus, which infected 11 passengers on a Dutch cruise ship, may have existed alongside humans for millennia. However, insights into human infections largely stem from a limited number of outbreaks over the past century.

The first recorded hantavirus outbreak occurred during the Korean War in the 1950s, impacting around 3,000 UN soldiers, who fell ill from a mysterious disease later identified as hantavirus.

It wasn’t until 1978 that scientists connected the virus to rodents in the Hantan River area of South Korea, leading to the naming of hantavirus.

In 1993, the first case was diagnosed in North America, followed by Argentina reporting the first known case of human-to-human transmission in 1996.

While hantaviruses are rare, they are significantly more lethal than respiratory viruses such as coronaviruses and influenza. Only one strain, not found in the continental U.S., can be transmitted between humans, linked to outbreaks on cruise ships that necessitated worldwide quarantines for passengers.

Previous limited cases of hantavirus infection provide insights into how cruise ship passengers fell ill, though medical experts assert that more research is needed.

“The study was exceptionally challenging due to the rarity of the disease,” stated Dr. Charles Chiu, a laboratory medicine and infectious diseases professor at the University of California, San Francisco.

Between 1993 and 2023, fewer than 900 hantavirus cases were reported in the U.S. Investigating each case can be complicated, as many patients succumb soon after symptoms develop, with fatality rates reaching up to 50% depending on the strain and transmission method.

“This recent outbreak will offer further insights, as we rarely encounter such a situation with more than a handful of cases,” noted Dr. Gregory Martz, professor emeritus of internal medicine at the University of New Mexico.

Below is an overview of significant hantavirus outbreaks in recent history.

Outbreaks in the Four Corners and Yosemite

In 1993, public health officials initiated an investigation into a mysterious outbreak in the Four Corners area of the United States, where Arizona, Colorado, New Mexico, and Utah intersect.

The first incident that raised alarms involved a 19-year-old distance runner from New Mexico, whose fiancée had recently died from an unexplained respiratory illness. He sought medical attention twice due to symptoms including fever, muscle aches, and gastrointestinal issues but was misdiagnosed and ultimately passed away just before his fiancée’s funeral.

“Some doctors recognized a pattern in multiple cases and suspected they were dealing with an unfamiliar illness,” commented Mertz, who contributed to the outbreak investigation.

The CDC later confirmed hantavirus via antibody testing and autopsy findings. At the time, it was unknown whether the virus infected humans in North America. This specific strain, named “Sin Nombre,” was linked to deer mice, which proliferated in the Four Corners region following an unusually wet spring. By August 1993, about 30 confirmed cases of infection were reported in the southwestern United States, 20 of which resulted in fatalities.