Matthew Pullen, MD: Understanding Hantavirus, Sin Nombre Virus, and the Emerging Andes Virus Threat

As concerns grow over reports of hantavirus infections linked to a cruise ship outbreak in South America, Matthew Pullen, MD, member of the Infection Control Today Editorial Advisory Board, says understanding the differences among hantaviruses is critical for healthcare professionals and the public alike.

During a recent interview with Infection Control Today, Pullen explained that hantavirus is not a single virus but rather a large family of viruses found throughout the world.

"Hantavirus is actually a very large family of viruses," Pullen said. "The name comes from the Hantan River Valley of South Korea, where one of the first members of this family was identified."

The viruses are generally divided into Old World and New World hantaviruses. In the United States, the virus most often associated with hantavirus infections is the Sin Nombre virus, which was first identified during a deadly outbreak in the Four Corners region of the Southwest in 1993.

"When you just say hantavirus, what you're really referring to is something called the Sin Nombre virus," Pullen explained. "It's fairly uncommon. We've only had about 800 cases in all of North America since it was discovered."

Sin Nombre virus is primarily spread through exposure to infected deer mice and their excretions. The rodents carry the virus without becoming ill themselves, creating opportunities for human exposure in rural settings where mice enter homes, sheds, and other structures.

Pullen also discussed the Andes virus, another New World hantavirus that has received increased attention following a recent outbreak investigation involving cruise ship passengers.

"The other New World hantavirus family member you hear a lot about right now is the Andes virus," he said. Unlike Sin Nombre virus, Andes virus has demonstrated possible person-to-person transmission in some outbreaks.

"There are a few instances where they're pretty confident there's human-to-human transmission," Pullen noted, although investigators have sometimes struggled to distinguish between direct transmission and shared environmental exposure.

Both viruses can cause hantavirus pulmonary syndrome (HPS), a severe disease with a case fatality rate of approximately 40%.

"It's a very serious disease," Pullen said. "You develop heart failure, respiratory failure, and capillary leak in your lungs."

The disease often begins with flu-like symptoms, including fever, headaches, muscle aches, nausea, and vomiting. Patients who progress to the cardiopulmonary phase can rapidly deteriorate as fluid accumulates in the lungs.

Recalling pathology findings from the original 1993 outbreak, Pullen noted the severity of pulmonary involvement. "The lungs were twice as heavy as normal lungs because they were just so bogged down with fluid," he said.

For infection preventionists, the key distinction remains that Andes virus is currently the only hantavirus known to have credible evidence of possible human-to-human transmission, making it a virus that warrants close monitoring as public health officials continue their investigations.