In this context, we would like to revisit our publication on hantaviruses that was published in August 2025, and can be accessed here: https://extension.arizona.edu/sites/default/files/2025-09/az2158-hantavirus-disease-prevention.pdf

Hantavirus and Disease Prevention

Shujuan Li¹, Dawn Gouge¹, Kathleen Walker¹, Kacey Ernst², Guillermo Adame³,
Irene Ruberto³, Shaku Nair¹, Al Fournier¹

¹University of Arizona, Department of Entomology (College of Agriculture, Life & Environmental Sciences). ²University of Arizona, Department of Epidemiology and Biostatistics (Mel and Enid Zuckerman College of Public Health),³Vector-borne and Zoonotic Diseases Program, Arizona Department of Health Services

Most hantavirus cases in the United States (U.S.) occur in western states and are often concentrated in the Four Corners region of the Southwestern U.S., this specifically refers to the region that connects Arizona, Utah, Colorado, and New Mexico. Hantavirus awareness increased during 2025 due to fatalities reported in California, Arizona, and the death of Betsy Arakawa, wife of the late actor Gene Hackman, from hantavirus in their Santa Fe home in New Mexico (CBS News, April 15, 2025, accessed August 2025). These tragedies have raised awareness about this rare but potentially deadly illness transmitted by rodents.

What are hantaviruses?

Figure 1. How people become infected by hantavirus.
Image credit: Excerpted from Centers for Disease Control and Prevention,
June 15, 2021, accessed August 2025.

Hantaviruses are a group of viruses that cause serious diseases and can be fatal. The viruses primarily infect rodents. People become infected through exposure to the urine, feces or saliva of an infected rodent. Most people get sick after inhaling virus-contaminated bodily fluids from rodents, their waste, or contaminated nesting materials. Rodent bites and scratches can also lead to transfer of the virus, as can consumption of contaminated food (Figure 1).

The hantaviruses that cause hantavirus pulmonary syndrome (HPS) are of the greatest concern to residents. In both Arizona and other contiguous states, the most common hantavirus strain is the Sin Nombre virus which can cause HPS. This virus is spread by deer mice in the genus Peromyscus. The hantavirus strain referred to as Seoul virus can cause hemorrhagic fever with renal syndrome. This is rare in the U.S. and has not been detected in Arizona.

The Centers for Disease Control and Prevention (CDC) report 864 cases of hantavirus infection nationwide between the beginning of surveillance tracking in 1993 and December 2022 (Figure 2, Centers for Disease Control and Prevention. June 26, 2024a, accessed August 2025). During January 2023 through December 2024 more than 60 additional cases have been reported by Health Departments in Arizona, Colorado, New Mexico, Washington, and California. Most hantavirus infections occur in states west of the Mississippi River. While human cases are considered rare, they can be fatal and approximately 1 in 3 people with HPS who develop respiratory symptoms die from the disease.

Figure 2. Map of U.S. Cumulative Cases of Hantavirus by State 1993 through 2022
that met the National Notifiable Diseases Surveillance System case
definition at the time of reporting, including 31 historical cases that occurred prior to 1993,
but were confirmed retrospectively. Five cases have presumed exposure outside the United States.
Image credit: Centers for Disease Control and Prevention (2024a),
accessed August 2025.

Where is hantavirus found in Arizona?

While hantavirus is found throughout the Southwestern U.S., it is especially prevalent in the Four Corners region where it was first identified in 1993. In Arizona there were eleven confirmed cases of hantavirus between 2016 to 2022, four of which were fatal. Most of the cases were in northern Arizona, with six in Apache County, three in Coconino County, one in Navajo County, and one in Maricopa County. Arizona experienced a spike in hantavirus cases in 2023 and 2024, with six and eleven confirmed cases, respectively. All but one person developed HPS and unfortunately six people died. Additionally, Pima County recorded the second case ever diagnosed in the county during 2024 (Arizona Department of Health Services (a), last accessed, August 22, 2025).

How is hantavirus spread?

Hantaviruses in the U.S. are not spread from person to person. Hantavirus is typically spread by wild rodents including deer mice (Figure 3), though multiple small mammal species, such as wood rats (Neotoma spp.) and hispid cotton rats (Sigmodon hispidus), can carry and shed virus in their saliva, urine, and droppings (Goodfellow et al. 2025).  The deer mouse Peromyscus maniculatus is most common in prairie, bushy, and woodland habitats (King 1968) throughout the region. The white-footed mouse (Peromyscus leucopus) is most abundant under 6,500-foot elevation, and the western deer mouse (Peromyscus sonoriensis) is considered to be a primary reservoir for the Sin Nombre virus (Goodfellow et al. 2025), in most areas, although more prevalent in the western and central areas of Arizona.

Figure 3. Adult deer mouse with distinguished identification features,
including the large ears and eyes and the clearly demarcated white underside
of the body and tail. 
Image credit: Jack Kelly Clark, University of California IPM program.

A person may be exposed to hantavirus by breathing contaminated dust after disturbing or cleaning rodent droppings or nesting materials. Living or working in rodent-infested settings increases the chance of exposure. A person can be exposed when entering unused buildings or coming into contact with rodent burrows outdoors. Rarely, individuals can be infected by consuming food contaminated with rodent urine or droppings or by being bitten or scratched by infected rodents (Arizona Department of Health Services (b), last accessed, August 22, 2025). Dogs and cats do not typically develop symptoms of illness when infected with Sin Nombre virus and cannot spread the virus directly to other animals or humans. However, they can put people at risk indirectly by bringing infected rodents into homes or buildings where exposure to infected rodent excretions may occur. Canines can be affected by other hantaviruses and develop illness.

Hantavirus pulmonary syndrome signs and symptoms

Hantavirus pulmonary syndrome is a severe and potentially fatal illness caused by some hantaviruses found in the Western Hemisphere. The viruses affect lung function, impacting breathing.

Early symptoms (usually 1-8 weeks after exposure) can include:

• Fatigue
• Fever
• Muscle aches
• Headaches
• Dizziness
• Chills
• Abdominal problems, like nausea, vomiting, diarrhea, and abdominal pain

Later symptoms (usually 4-10 days after the initial phase of illness) include:

• Coughing and shortness of breath

• Tightness in the chest, as the lungs fill with fluid

   

  Treatment and recovery

• If you believe you may be experiencing symptoms of hantavirus, or been exposed to the virus, seek medical care.
•  There are currently no U.S. Food and Drug Administration-approved hantavirus vaccines available in the United States. There are no specific or antiviral medications for infections. Treatment focuses on supportive care to manage symptoms and maintain organ function until the body can fight off the virus. This often involves intensive care in a hospital setting, which may be crucial for recovery. 
• Early symptoms are often non-specific and mimic other viral illnesses, making diagnosis challenging. HPS diagnosis relies on a combination of clinical evaluation, history of potential rodent exposure, and laboratory tests. Testing for hantavirus antibodies in the blood is the primary diagnostic tool. The CDC uses an enzyme-linked immunosorbent assay to detect IgM antibodies and diagnose acute infections of hantaviruses.

How to prevent hantavirus infection?

The best way to prevent hantavirus infection is to avoid exposure to rodents, their urine and feces. You can concurrently seal up to prevent rodents from entering buildings, clean up to remove contaminated waste, and “trap up” to reduce rodents in buildings (Figure 4) (Centers for Disease Control and Prevention, 2021, accessed August 2025). 

Figure 4. https://www.cdc.gov/hantavirus/media/pdfs/2025/01/HantavirusBrochure-508.pdf?utm_source=substack&utm_medium=email

In summary

• Hantavirus is transmitted when humans come into contact with infected rodents and their feces, urine, and saliva.
• You can get infected by breathing dust that has been contaminated with hantavirus, being bitten or scratched by infected rodents, or on rare occasions consuming contaminated food.
• Immediate supportive care is essential to save lives.
• Approximately 1 in 3 people with hantavirus pulmonary syndrome die, so do not delay seeking medical care.
• Hantavirus infection is preventable by taking precautions when cleaning and entering spaces where rodents have been recently occupying. Hantaviruses do not persist for long periods of time in warmer temperatures, but it is often impossible to know when an infected rodent was last in a building.
• DO NOT sweep or vacuum rodent urine, droppings, or nesting materials. It can stir up the virus in airborne particles that may be inhaled.
• Take precautions when handling a dead rodent. Safely dispose of dead rodents. Clean up and disinfect areas contaminated with rodent urine and droppings.

Check out our publication linked here for the above information and more!

What the Heck Was This? (From our March issue)

 

Answer: Non-biting midge.

Congratulations to Master Pest Detective:

Christine Del Re, Maricopa County Master Gardener

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What the Heck is This?

 

Photo by Kyle Kelly.

If you know the answer, email Shaku Nair at nairs@arizona.edu.
You will not win anything if you are correct, but you will be listed
as a “Master Pest Detective” in the next
newsletter issue.

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