The Norway rat (Rattus norvegicus) is a familiar urban pest, and Hantavirus is a group of viruses that can cause severe, sometimes fatal, illness in humans. Public concern about this common rodent carrying such a serious disease is understandable, especially when infestations occur in homes or workplaces. While the virus is rare, the pulmonary form of the disease has a high fatality rate, making accurate information about transmission sources important. This article clarifies the specific role of the Norway rat regarding Hantavirus and identifies the primary carriers of the infection.
Are Norway Rats Hantavirus Carriers?
Norway rats are not the primary source for Hantavirus Pulmonary Syndrome (HPS), the severe respiratory illness most commonly associated with the virus in the Americas. The strains of Hantavirus that cause HPS, such as Sin Nombre virus, have specialized relationships with specific native rodent species. These pairings mean the common urban Norway rat poses a very low risk for transmitting HPS.
The Norway rat is a known carrier of a different hantavirus strain called Seoul virus (SEOV). Seoul virus is an “Old World” hantavirus found globally that causes a different illness in humans called Hemorrhagic Fever with Renal Syndrome (HFRS). While HFRS is less severe than HPS, it can still cause kidney problems and is a concern for those who handle wild or pet Norway rats. Understanding this distinction is important, as the risk is not zero, and the threat is to a different organ system than the lungs.
Identifying the Primary Rodent Reservoirs
The greatest risk for Hantavirus infection in the Americas comes from native rodents that act as the true reservoir hosts for the “New World” strains causing Hantavirus Pulmonary Syndrome (HPS). A reservoir host carries the virus without displaying symptoms, shedding it through urine, feces, and saliva. The virus’s geographic distribution is directly tied to the range of its specific rodent host.
In North America, the deer mouse (Peromyscus maniculatus) is the most significant carrier, primarily transmitting the Sin Nombre virus. Other native carriers include the cotton rat and the rice rat in the southeastern United States, and the white-footed mouse in the Northeast. In South America, the long-tailed pygmy rice rat (Oligoryzomys longicaudatus) is the main carrier, responsible for transmitting the Andes virus.
The risk of contracting HPS is highly dependent on exposure to these specific wild, non-urban rodents, particularly in rural or semi-rural settings like barns, sheds, or cabins. These reservoir species are distinct from the common urban Norway rat and house mouse, which have never been known to transmit HPS.
Transmission Routes and Human Infection
Hantavirus transmission occurs primarily through inhaling aerosolized particles containing the virus. When dried rodent droppings, urine, or saliva are disturbed, tiny particles become airborne and are breathed into the lungs. This is the most common way people become infected, often occurring when cleaning areas that have been closed up for a long time.
Less common routes include direct contact with fresh rodent excretions, touching a contaminated surface before touching the eyes, nose, or mouth, or being bitten by an infected rodent. Once inhaled, New World hantaviruses cause HPS, which begins with flu-like symptoms such as fever, muscle aches, and fatigue. The illness can rapidly progress to respiratory failure as the lungs fill with fluid, and HPS has a fatality rate of nearly 40%.
Essential Prevention and Safety Measures
Preventing Hantavirus infection centers on avoiding contact with rodents and safely cleaning up contaminated areas. Never sweep, vacuum, or dry-dust rodent droppings or nesting materials, as these actions create the dangerous aerosolized particles that transmit the virus. The area must be well-ventilated for at least 30 minutes before cleanup by opening doors and windows.
Personal protective equipment (PPE) is necessary, including rubber, latex, vinyl, or nitrile gloves. Contaminated areas must be thoroughly wet down with a disinfectant solution, such as a mixture of one part bleach to nine parts water.
Cleanup Steps
- Allow the solution to soak for five to ten minutes.
- Use paper towels or disposable rags to wipe up the materials.
- Place the materials in a sealed bag and discard them.
- Wash gloves with disinfectant or soap and water before removal.
- Follow up with thorough hand washing.