Hantavirus Strains: Understanding Your Specific Risk Profile

When you are diagnosed with Hemorrhagic Fever with Renal Syndrome (HFRS), your recovery and symptoms depend significantly on which strain of hantavirus you have. These viruses are often “neighborhood-specific,” meaning they live in certain types of rodents that are only found in specific parts of the world ^[1][2]. It is always helpful to ask your doctor which strain is most prevalent in your local area, as this will guide their expectations for your care.

The Four Main Strains

There are four primary viruses that cause HFRS. Knowing which one you have can help you and your doctor understand what to expect during your hospital stay ^[2].

Nephropathia Epidemica (Puumala Strain)

If you are in Europe or Scandinavia and catch the Puumala virus, your illness is often called Nephropathia Epidemica (NE) ^[1].

• A Milder Course: NE is generally the mildest form of HFRS ^[3]. While it still causes fever, headache, and kidney stress, it rarely causes the severe bleeding or extreme low blood pressure seen in other strains ^[4].
• Vision Changes: A unique symptom often reported with the Puumala strain is a temporary change in vision, such as sudden nearsightedness or “floaters,” because the virus can cause the eyes to swell slightly ^[5].
• Low Mortality: The risk of death from NE is very low (usually less than 0.1%), and most patients recover fully without long-term kidney damage ^[3].

The Moderate Profile: Seoul Virus

The Seoul virus is unique because it is carried by the common brown rat, which lives near humans all over the globe ^[6].

• City Exposure: Unlike other strains that are mostly caught in the woods or on farms, Seoul virus is often caught in urban areas ^[6].
• Liver Involvement: In addition to kidney stress, the Seoul strain is more likely to cause mild inflammation of the liver (hepatitis). Your doctor may notice this as a rise in “liver enzymes” on your blood tests ^[7][8].

The Severe Profiles: Hantaan and Dobrava

The Hantaan and Dobrava strains are the most serious forms of HFRS and require intensive medical monitoring ^[2].

• High Risk of Complications: These strains are much more likely to cause the “triad” of severe symptoms: high fever, significant internal bleeding (hemorrhage), and acute kidney failure ^[3][9].
• Higher Mortality: Mortality rates for these strains can range from 5% to 15% depending on the region and the level of medical care available ^[9][3].
• Intensive Support: Patients with these strains are more likely to require temporary dialysis or blood pressure support in an Intensive Care Unit (ICU) ^[10].

Factors That Affect Your Personal Risk

While the strain is the biggest factor, other things about you can change how the virus affects your body:

• Age: Older adults are generally at a higher risk for a more severe course of the disease ^[11].
• Underlying Health: Having pre-existing kidney issues, heart disease, or high blood pressure can make the “vascular leak” phase of HFRS more difficult to manage ^[12].
• Genetics: Researchers have found that certain genetic markers in your immune system may make you more or less likely to have a severe reaction to the virus ^[13].