A Brief Overview of Hantavirus

by Mary Nell Wegner

Hantavirus is a rare disease for which there is no current vaccine, specific treatment or cure. It is part of a larger family of hantaviruses largely spread by rodents; in the Southwest, the rodent that carries hantavirus is the deer mouse, which is typically small with big eyes and ears and a white belly. Through their saliva, droppings, and urine, deer mice can transmit the virus to humans.

Once infected, an individual is at risk for developing hantavirus pulmonary syndrome or HPS, which affects the lungs and can become fatal. However, a person may become infected and not progress to HPS—instead exhibiting flu-like symptoms that do not go on to invade the cardiopulmonary system. For these people, hantavirus is likely experienced as something that simply makes them feel crummy, with severe fatigue and muscle aches. Also, up to 30% of people testing positive for hantavirus will have no symptoms whatsoever.

For the family of hantaviruses endemic to the Americas, all have the potential to progress to HPS, but not all cases do. (Interestingly, in other places in the world, a related hantavirus,  hemorrhagic fever with renal syndrome (HFRS), sidesteps attacking cardiopulmonary functions and, instead, attacks the kidney.)

Hantavirus was discovered relatively recently. In 1993, the Centers for Disease Control and Prevention sent a team from their Epidemiology Intelligence Service to the Four Corners area to investigate what was causing relatively young, healthy people to die from a rapidly progressing pulmonary disease. One of the officers on the case, Dr. Jeff Duchin, remembers working closely with a team of clinicians in New Mexico to try to understand why “…young, healthy people were dying from this rapidly progressive pulmonary disease with no other explanation…[it]… really set off alarm bells.” 

While hantavirus is not always severe or fatal, historically, about 40% of those sick enough to land in the hospital – and, therefore, to have their cases documented – died from it. In all likelihood, the vast majority of people infected by hantavirus have mild cases and are never diagnosed. In the 1993 outbreak, 14 people died. From 1993 to 2022, New Mexico had 129 of the 864 confirmed cases in the United States. The state had seven known cases in 2023 and another seven in 2024. To date, there has been one hantavirus fatality in 2025 in New Mexico.

Hantavirus pulmonary syndrome progresses in a similar fashion to COVID. Large amounts of  inflammatory chemicals (cytokines IL-6 and TNF-a) are released from muscle tissue. These chemicals cause damage to the cells in the lining of the vascular system resulting in fluid in the lungs and a “ground glass” appearance on chest x-rays similar to COVID. Physicians typically identify the syndrome when a patient has low oxygen saturation and chest x-ray or ultrasound findings characteristic of viral infection. Typically, hantavirus pulmonary syndrome is treated in an intensive care unit with continuous positive pressure (CPAP) and steroids. 

Suspicion of Hantavirus

If someone is suspected of hantavirus exposure, somewhat counterintuitively, the first step is not to test for the virus (as for COVID or the flu), but rather to monitor oxygen saturation. Unlike COVID, hantavirus is not contagious and critical treatment is only advantageous to the individual if there is an onset of the pulmonary syndrome. As such, an oxygen saturation rate below 92 should be cause for further evaluation with a health care provider and, in these cases, individuals are typically admitted to the hospital and treated with continuous positive pressure (CPAP) and steroids.

The best prevention is avoiding contact with rodents and their droppings – and if you feel you’ve been exposed, you can easily measure blood oxygen saturation at home with an inexpensive monitor. If your oxygen saturation has fallen below 92, call your provider immediately and seek care. Pulmonary illness can come on quickly.

Read 10 Practical Considerations for more.