Hantavirus is a group of viruses carried by rodents that can cause severe illness in humans. The most commonly recognized form in the Americas is Hantavirus Pulmonary Syndrome (HPS). HPS is a severe respiratory disease that rapidly progresses from mild symptoms to life-threatening respiratory failure. The high case fatality rate, often between 30 and 40 percent, underscores the seriousness of contracting the infection.
The Actual Incidence Rate
Hantavirus Pulmonary Syndrome is statistically a rare disease in the United States. Since surveillance began in 1993, a total of 864 hantavirus disease cases were reported through the end of 2022. The average number of confirmed cases nationwide is fewer than 30 per year.
The low incidence rate is tied to the specific and limited conditions required for human exposure. Hantavirus is contracted exclusively through contact with infected rodents or their waste products. The vast majority of cases, approximately 96%, have been identified in states west of the Mississippi River, where the primary rodent carriers are most prevalent. The Sin Nombre virus (SNV), which causes most HPS cases in the U.S., is carried asymptomatically by the deer mouse (Peromyscus maniculatus). Exposure requires a person to be in an enclosed space with a high concentration of aerosolized virus, which keeps the overall case numbers low.
Specific Transmission Pathways
Infection occurs when a person inhales aerosolized particles containing the virus shed by infected rodents. These microscopic particles are found in the urine, droppings, and saliva of the carrier animals. The virus does not typically spread through direct person-to-person contact, making it solely a zoonotic disease.
The most common pathway for aerosolization happens when contaminated areas are disturbed, causing dried rodent waste to become airborne dust. This often occurs when people clean out infrequently used structures like sheds, barns, or vacant cabins where rodents have nested. Sweeping or vacuuming dry materials in these enclosed spaces can create a cloud of virus-laden dust that is easily inhaled.
While the deer mouse is the main reservoir for the Sin Nombre virus, other hantavirus strains are associated with different specific rodent hosts. For example, the cotton rat (Sigmodon hispidus) is the primary carrier for the Black Creek Canal virus. Transmission to humans is an accidental spillover event from this animal reservoir.
Recognizing the Symptoms and Disease Progression
The progression of HPS can be divided into two distinct clinical phases, beginning after an incubation period that can range from one to six weeks post-exposure. The initial stage is known as the prodromal phase and typically lasts for three to seven days. Symptoms during this period are non-specific and easily mistaken for common viral illnesses, including fever, chills, severe muscle aches, headache, and sometimes gastrointestinal issues.
Following the prodromal phase, the illness enters the dangerous cardiopulmonary stage, which can progress rapidly over a matter of hours. This phase is characterized by the sudden onset of respiratory distress, marked by shortness of breath and a persistent cough. The virus primarily targets the endothelial cells lining the small blood vessels, leading to a condition called capillary leak syndrome. This allows large amounts of fluid to leak from the bloodstream into the lungs, resulting in noncardiogenic pulmonary edema. This fluid buildup impairs the body’s ability to oxygenate the blood, leading to severe hypoxemia and, in severe cases, shock.
Essential Prevention Strategies
The most effective way to prevent hantavirus infection is to minimize exposure to rodents and their droppings, especially in enclosed spaces. Before beginning any cleanup in an area with potential rodent infestation, the space should be ventilated by opening all doors and windows for at least 30 minutes to allow any airborne particles to dissipate. A wet cleaning method must be used to prevent dried droppings and urine from becoming aerosolized. Never use a broom or a standard vacuum cleaner on rodent-contaminated areas.
Instead, spray the contaminated materials and surfaces thoroughly with a disinfectant solution, such as a mixture of one part bleach to nine parts water, and let it soak for at least 10 to 15 minutes before wiping it up. Personal protective equipment is necessary for safe cleanup, including rubber or plastic gloves. For areas with heavy contamination, a high-efficiency particulate air (HEPA) filtered respirator, such as an N95 mask, should be worn. All cleaning materials, droppings, and dead rodents should be double-bagged and sealed before being placed in the trash.